Home

User`s Manual - waynejones.net

1. OF PLAY manual control setting 81 PLAY measurement path 37 PLAY path results 98 PLAY sample rate error 39 PUGS xa care ce a we a 106 107 Printing reports 24 644 6 2s wale a E E dd md 67 Protocol verification 64 R RCA plugs andjacks 107 RECORD manual control setting 83 RECORD measurement path 53 RECORD path results 101 RECORD PLAY LOOP measurement path 60 RECORD PLAY LOOP path results 103 Remote testing 69 76 See Also DCOM Hardware connections 75 Remote testing requirements 69 Reports DUNN sane da as ee ke HS 67 EDOFS XML a as a nla Se E 67 Resolution setting 23 Results displaying sa oaa mm dis di ao do ae a 66 reporting ssa sm a dE we E wd 67 SAVING sa ma de Rc Bas ae E O A 66 VW s s ee a naa E a ah a 65 Results Viewer 2 000 65 Running tests aca ia al Go Be ae A 36 S S AES17 filter use with PC Audio Test 4 Sample rate setting 23 Security property forDCOM 13 Signal to Noise Ratio 49 Slider position 44 4 41 Sliders ASSINO e a s sasereg we EG 20 Position oaoa a a a a 41 SNR See Signal to Noise Ratio Software installation 13 Status indicators 36 Switcher aooaa a a a ee
2. 103 DIGITAL LOOP D D Path Results 104 Appendix C Connector Designations 2004 105 Balanced and unbalanced connections 105 Male and female plug and jack 02 0048 105 3 5 mm plugs and jacks i wt pas dd 6 eR ew Re ee 106 Ya phone plugs and jacks 2 a a 106 RCA or phono plugs and jacks 107 XLR Connectors ourense E SA E 108 BNC connectors a a a a a a 108 Optical connectors aooo a a a 109 Fan out connections 2 oaoa a e a DE RES O RA E 109 Digital Connections lt sas sa s a d e ra raoa e a aaa 109 Grounding 62466445 Soe ee a DAS ASAS e pee 110 Instrument Analog Connections a e a a a 2585084 110 Instrument Digital Connections oaoa a a a a a a a 110 Using a Switeh er i s sics ain pega hee ee A 110 Appendix D Glossary 2 aa a a a 113 Appendix E Bibliography 3 3 mios ea aaa 121 Audio Standards a a a 121 Audio Test and Measurement a eee 121 DOOM gs ee wae ee ee ae eee oo ss RE RA 121 Audio in Personal Computers 2 2 0 00000 eee ene 122 PC Audio Test User s Manual Contents Contents vi PC Audio Test User s Manual Introduction Welcome to Audio Precision s APP 2010 PC Audio Test Included with the application software CD ROM 1s this user s manual and a set of four ca bles
3. 22 008 Mic Bias MeasurementS ee THD N measurement 0 0 0 0 a a a a a Dynamic Range measurement oaoa a a a e a eae Signal to Noise Ratio measurement Frequency Response measurement a a a RECORD Measurement Path Introduction to RECORD A D PC path aoaaa AD E Stimulus signals forthe RECORD path Level Reference measurement a Do RECORD Level Reference FIRST Line In Recording Slidersetting THD N measurement a 2 a a a Dynamic Range measurement a a a a a a a a Frequency Response measurement Passband Ripple measurement aoa aa a a a a a a 2 550088 MIC RECORD MeasurementPatb Introduction to MIC RECORD A D PC path sss u s secim dga E ARES E BE id A Stimulus signals for the MIC RECORD path Level Reference measurement a a a a Mic In Recording Slider setting 4 THD N measurement aoao a a a Dynamic Range measurement a a a a a a a a ee ee Frequency Response measurement a oaoa oaoa a a a a a a a a a Passband Ripple measurement oa oaoa a a a a a a a a a a RECORD PLAY LOOP Measurement Path PC Audio Test User s Manual Contents Contents Introduction to RECORD PLAY LOOP A D PC D A path e
4. 102 PC Audio Test User s Manual RECORD PLAY LOOP A D PC D A Path Results Appendix B Results Listings RECORD PLAY LOOP A D PC D A Path Results Description Collection Name Data Type Formatting Unit ADDATHDTsicond___ Str mw RIP LOOP Dynamic Range test conditions ADDADynRngTsiCond__ Str no f RIP LOOP Max Pos Phase Error ADDAPhaseMax Sr 0 000 deg RIP LOOP Max Neg Phase Error ADDAPhaseMin Sr ko00 degr R P LOOP Frequency Response Ch B bl array no BV R P LOOP Frequency vs Relative Phase bl array no R P LOOP Frequency Response test conditions no R P LOOP Frequency Response Limit tr no PC Audio Test Users Manual 103 Appendix B Results Listings DIGITAL LOOP D D Path Results DIGITAL LOOP D D Path Results o Desoription ColectonNamo DataType Formatting Unit DOuISR DD LOOP Digtal nterface Output Flag Erors Jodourigs To D D LOOP Digital Interface Output Stat bits summary DDOutStatBit fs fo DSRC sr Jo o D D LOOP Output Bit Validity DDBitOutvalid Sr fo DDBItOutValidSR___ St 104 PC Audio Test User s Manual Appendix C Connector Designations Balanced and unbalanced connections m Unbalanced For these purposes unbalanced refers to inputs outputs and interconnections that use only two conductors One conductor carries the signal high and the other conductor carries the signal low The low conductor is almost always grounded at one or both ends of the inte
5. Audio Precision Hardware Instrument Switcher Line or Spkr Out to 1 amp 2 ha From Unbal Float 1 amp 2 v from Bal Float 1 amp 2 to BNC unba w 1 amp 2 from BNC unbal 1 amp 2 Figure 16 DUT instrument connection and switcher assignments The top area of the DUT Configuration panel enables you to assign the Au dio Precision instrument ports and switcher channels to the DUT input an out put ports The DUT Line Out Speaker Out ports for example can be assigned to the instrument BNC Unbal or XLR Bal analyzer inputs In a similar fashion you can assign the other DUT ports to the available instrument ports 18 PC Audio Test User s Manual DUT Selection and Configuration Chapter 2 Getting Ready NOTE You must be sure that your cable interconnections match the software selections you have made on this panel The Connection Assignments feature only informs the instrument or switcher of your port choices If you are using an Audio Precision switcher such as an SWR 2122 series switcher as a component of a PC sound device test you can select which pairs of switcher channels are assigned to your DUT input or output ports Ground Check In any system of audio devices good interconnection practice is essential to maintain signal integrity Connections with inadequate shielding high imped ance ground paths or the multiple ground paths called ground loops can in troduce hu
6. precision PC Audio Test User s Manual Installation and Operation of APP 2010 PC Audio Test Audios precision Copyright 2004 Audio Precision Inc All rights reserved Audio Precision part number 8211 0176 rev 1 No part of this manual may be reproduced or transmitted in any form or by any means electronic or mechanical including photocopying recording or by any information storage and retrieval system without permission in writing from the publisher Audio Precision System One System Two System Two Cascade System One DSPM System Two DSPM Dual Domain FASTTEST APWIN ATS and ATS 2 are trademarks of Audio Precision Inc Windows is a trademark of Microsoft Corporation Published by 5750 SW Arctic Drive LI IO E iii Beaverton Oregon 97005 o HT Tel 503 627 0832 Fax 503 641 8906 US Toll Free 1 800 231 7350 email info audioprecision com Web audioprecision com Printed in the United States of America 1V0216115900 Chapter 1 Introduction clcll a 1 Overview gt ec bx bE BE ee eGR ERE 1 Measurement Instrument Requirements 3 Recommended Instrument Analyzer Filters 3 Option Filters a0 lt lt a a A A A 4 S AES17 Filter cbc oa aa a 4 Basic Configurations seas 48 RELEASE S ER 4 QUIETO eso eee he ee eee E E E A Sd 6 Device Under Test DUT 2 0204 6 Paths
7. PC Audio Test User s Manual 31 Chapter 2 Getting Ready Connecting the Hardware 32 XLR FEMALE XLR MALE Shield not connected is end at this Figure 32 PC Audio Test Mic Bias cable wiring Ground Cable The ground cable has a clip at the DUT end for attachment to the computer chassis and a banana connector at the instrument end for insertion into a ground lug marked with the symbol shown here in the margin PC Audio Test User s Manual Running the Tests Introduction The group of measurements performed by PC Audio Test 1s called a test A test can include measurements of all the key parameters of a DUT in all avail able measurement paths or 1t can be restricted to measure only a few parame ters 1n a restricted set of paths This chapter describes how to select measurement paths and specific mea surements and perform tests on your DUT Your configuration settings and results are saved as part of the test procedure m DUT configuration see page 16 is saved in a cfg file m Test settings see page 22 are saved in a set file m Test results see page 66 are saved in a xml file Before a test can be successfully run you must be sure that the DUT hard ware and your Audio Precision instrument are properly connected and that the instrument and DUT software controls are properly configured Connections and configuration are described in Chapter 2 XML tag notation in this chapter
8. m The Windows Autorun features should automatically open the installation menu shown in Figure 12 If Autorun is not enabled on your APP 2010 Ca Install APP 2010 Software e Manuals and Documentation J g quick Start Cuide E Figure 12 APP 2010 PC Audio Test Installation Screen PC Audio Test User s Manual 13 Chapter 2 Getting Ready Installing the Software 14 computer click the Start button on the Windows taskbar Then click Run and type D Setup and then OK where D is the drive letter of the CD ROM drive The installation menu offers 4 choices Install APP 2010 Software Click Install APP 2010 Software to begin installation NOTE APP 2010 PC Audio Test requires the correct version of Audio Precision control software to be installed on the computer that is controlling your Audio Precision instrument see the table on page 3 If you do not already have the correct control software installed on your computer be sure to install it now before running PC Audio Test Manual and Documentation Click Manual and Documentation to open a pdf menu listing user documentation for PC Audio Test with links to user documentation pdfs on the CD ROM Quick Start Guide Click Quick Start Guide to open the PDF version of the Quick Start Guide included with PC Audio Test m Exit Click Exit to leave the installation program PC Audio Test User s Manual Launching APP 2010 PC Audio Test Chapter 2
9. 0 050 ee eee 40 Frequency Response measurement 0204 40 Passband Ripple measurement 2 208 41 ANALOG LOOP Measurement Path 42 Introduction to ANALOG LOOP A A path 2 A 42 Stimulus signals for the ANALOG LOOP path 42 Level Reference measurement 42 Unity Gain Setting a a a a a a a 0 0 00 00 eee eee 42 Level Reference with Unity Gain selected default 43 PC Audio Test User s Manual Level Reference with Unity Gain deselected THD N at ANALOG LOOP Level Reference Line In Level measurement Line In Slider setting 22 2 24 e4 Kee 244444 4 THD N measurement 2 2 0 eee Dynamic Range measurement 2 2 a ee eee Signal to Noise Ratio measurement Frequency Response measurement 2484 Crosstalk measurement 2 eee ee MIC ANALOG LOOP Measurement Path Introduction to MIC ANALOG LOOP A A mic path 22 esse eee eee es Pee ee ewe RRR Dee EA Using the Mic Bias cable 2 0 200004 Stimulus signals for the MIC ANALOG LOOP path Level Reference measurement 00 2 2 ee a THD N at MIC ANALOG LOOP Level Reference Mic In Level measurement 0 0 0 0 04 Mic In Slidersetting 0 0 00 00 ee a Mic Boost Gain measurement
10. 02 0048 76 Appendix A Troubleshooting 0 0 eee T7 Compatibility with Windows APIS a a a a aa 0 2 05 4 0 17 The Windows Mixer API o TT Special Run Modes for PC Audio Test 78 Alie i lt a dev rsss E ee E E E 78 AllMax o Pee eee ee bee eee 78 Manual Override a a a 79 Test Failures s kt ooo a essere 79 Connection and Configuration oaoa aa a a a 79 Eric AEREA 80 Level Reference Failures 2 80 IV PC Audio Test User s Manual Manual PLAY level control setting 81 Manual ANALOG LOOP level control setting 82 Manual RECORD level control setting 83 Test Messages 85 General 23234644628 bee 5652 bee eee eee SG Oe 85 D ALevelR f a a a a a a a 87 A A LevelRef aoaaa aa a a a a 89 Mic A ALVMIRef a a 91 A D LevelR f a 92 Mic A D LevelRef e 94 Appendix B Results Listings aoaaa e o 97 MUOU Oe 22 24 SD sosa rasa A 97 PLAY D A Path Results 98 ANALOG LOOP A A Path Results 99 MIC ANALOG LOOP A A Path Results 100 RECORD A D Path Results 101 MIC RECORD A D Path Results 102 RECORD PLAY LOOP A D PC D A Path Results
11. 49 Chapter 3 Running the Tests Mic In Bias Current lt MiclnSupplyl gt MIC ANALOG LOOP Measurement Path bias current available on the ring connection In addition to testing the Mic In audio performance PC Audio Test can measure both the bias voltage and the bias current under conditions comparable to a nominal load This is made easy using the Mic Bias cable provided with PC Audio Test The Mic Bias cable provides a female XLR for connection to the Audio Preci sion instrument Analog Output and a male XLR for connection to the instru ment Analog Input for Mic Bias measurement See page 30 and Figure 37 below Mic Bias Cable Analog Audio Jo E or 00 Oo Oo UTB Boo 230 00 o O 0 0 O o ELA CHANNEL GENERATOR AUX SIGNALS A UN O mea fo 009 Fea Audio Precision Instrument Ground Connection Figure 37 Connections for MIC ANALOG LOOP with Mic Bias cable MORA THD N measurement lt AAMicT HDA gt lt AAMicT HDB gt 50 See the Distortion THD N sidebar on page 44 For the MIC ANALOG LOOP THD N measurement PC Audio Test ap plies a 997 Hz sine wave to the Line In jacks Depending on your configura tion settings the stimulus level may be at O dB 1 dB 3 dB 6 dB or ata level of your choice relative to the DUT Analog Input Level AES17 specifies the 1 dB stimulus level
12. 3 designates the number of conductors With three conductors XLR connectors are usually used as single channel balanced connectors AES3 specifies XLR 3 type connectors for professional digital audio intercon nection BNC connectors iii Figure 62 BNC connectors BNC connectors have two conductors and are used for single channel un balanced connections BNC connectors are found on test and measurement equipment and in professional television and video applications BNCs are the standard connector for AES31d digital audio interconnection 108 PC Audio Test User s Manual Optical connectors Appendix C Connector Designations Optical connectors Figure 63 Toslink optical connectors Some PC sound devices provide digital output or digital input and output as an optical signal typically at one or two Toslink connector jacks Fan out connections Figure 64 A typical fan out connector For PC sound devices that are specified with many multitrack or large XLR connectors a multipin connector with a fan out cable may be provided Digital Connections Most PC sound devices currently manufactured do not include digital input or output capabilities More and more are adding digital output only and a few professional and semi pro products have both digital output and input These digital signals may be carried electrically in the S PDIF format on unbalanced 3 5 mm jacks or RCA jacks or may be carried opt
13. Check Test Settings for correct Sample Rate Messages like the one above can appear at various places within the mea surement procedure The specified frequency here shown as 997 Hz may be different depending on the test requirement This message usually means there is a disagreement between the sample rate set on the DUT Configuration panel and the sample rate of the requested waveform file or it may mean no signal which usually means a connection problem a DUT or instrument configura tion problem or an extra DUT software driver mixer control that is not enabled ERROR Reference waveform agm file Not found for cur rent sample rate The above message reflects a Test Settings setup error or a missing file It means that no level reference file exists for the sample rate you specified on the Test Settings panel This message appears with the first test after the erro neous Test Settings entry ERROR Passband Ripple test waveform agm file Not found for current sample rate PC Audio Test User s Manual Test Messages Appendix A Troubleshooting The above message reflects a Test Settings setup error or a missing file It means that no passband ripple file exists for the sample rate you specified on the Test Settings panel This message appears with the first passband ripple test after the erroneous Test Settings entry ERROR Ap Generator Regulation Error Err Number Err Description The above
14. In its local configuration PC Audio Test performs measurements on the sound device installed in the PC running the Audio Precision control software See Figure 1 for a system diagram 1n local configuration A remote configura tion enables PC Audio Test to perform the measurements on a PC audio device PC Audio Test User s Manual Chapter 1 Introduction Overview Audio Precision Instrument APIB Audio IN cfg DUT Configuration File AP Control DUT Software DS set PC Audio Test Tesi Software Settings File Personal Computer ES la xml htm Results Report Report File File File other formats Figure 1 PC Audio Test system diagram local configuration installed on a remote target computer See Chapter 5 for information on us ing PC Audio Test in remote configuration Results are saved as XML text which enables you to design custom reports that select and format the results for any purpose NOTE PC Audio Test does not evaluate the MIDI or audio synthesis capabilities of any sound device 2 PC Audio Test User s Manual Measurement Instrument Requirements Chapter 1 Introduction Measurement Instrument Requirements To run the tests PC Audio Test requires m an Audio Precision measurement instrument such as System Two System Two Cascade or a 2700 series instrument for full PC Audio Test functionality the instrument must have analog and digital
15. PC Audio Test User s Manual 41 Chapter 3 Running the Tests ANALOG LOOP Measurement Path 42 ANALOG LOOP Measurement Path lt o LINE IN MIXER PLAYBACK PLAYBACK EINE GUT LINE IN MASTER or SLIDER VOLUME SLIDER Figure 35 ANALOG LOOP path block diagram Introduction to ANALOG LOOP A A path In ANALOG LOOP the PC audio device buffers and sets the level of the analog audio presented at the Line input and then routes the signal through the playback mixer and to the device analog outputs If there is no Line Input the MIC ANALOG LOOP must be used Stimulus signals for the ANALOG LOOP path For both single tone and multitone ANALOG LOOP measurements PC Audio Test controls the instrument analog generator providing the appropriate analog stimulus signal for each measurement Level Reference measurement The ANALOG LOOP Level Reference is the output voltage measured at the analog outputs when the ANALOG LOOP path Level Reference criteria are satisfied See the Level Reference sidebar on page 38 Unity Gain Setting It is possible to measure ANALOG LOOP Level Reference under two con ditions with unity gain forced the default PC Audio Test setting and without unity gain forced See Test Settings on page 22 PC Audio Test User s Manual ANALOG LOOP Measurement Path Chapter 3 Running the Tests dBr Audio Precision instruments use a unit called the dBr as a reference for rel ative meas
16. This message is the same as the previous message but is the result of a dif ferent single step minimization routine CAUTION Levels are Out of Balance more than one slider step 0 0 dB This message notes a balance offset of more than one slider step At this point in the test the pan or balance controls have been checked so the problem is likely due to analog circuit imbalance In DUTs with very fine slider resolu tion this caution may not be important A A LevelRef DUT Configuration Line In control selected is a Microphone control type Use anyway Some DUTs use the same physical connections and mixer controls for Line In and for Mic In When this setting 1s selected PC Audio Test checks to be sure it 1s not a mistake PC Audio Test User s Manual 89 Appendix A Troubleshooting Test Messages Manual Line In A A slider and Generator Amplitude Adjust Last Measurement Chan A 0 00dBV THD 0 00 Chan B 0 00dBV THD 0 00 If Distortion is high and Level low reduce Generator output If Level and Distortion are low increase Input A A Manual Override Set slider control for maximum level and THD lt 1 Take a new measurement The above message appears during the ANALOG LOOP manual override level setting procedure This dialog reports the current level and distortion and with the control software displays is an aid to DUT control adjustment Click YES to submit a new setting o
17. decibels relative to a signal level of 0 7746 V rms dBu now is the common term for analog audio amplitude in professional audio interfaces and circuits O dBu 0 7746 V rms equals O dBm but only in a 600 ohm load im pedance Unless you are clearly interested in measuring power in a circuit of known impedance use dBu not dBm See dBm dBV decibels relative to a signal level of 1 volt rms dBV now 1s the common term for analog audio levels in consumer audio interfaces and cir cuits 0 dBV equals 2 218 dBu D D Abbreviation for Digital Digital measurement path Commonly re ferred to in PC Audio Test as the DIGITAL LOOP measurement path digital overflow see digital clipping digital recording or processing a technique in which the original signal is periodically sampled and the amplitude value at each sampling instant is converted into a number represented by a binary word digital to analog Abbreviated D to A D A D A and so on See digital recording or processing and digital to analog converter digital to analog converter a device that converts a stream of digital numbers each representing the amplitude of a signal at a particular sampling time into a corresponding analog signal Abbreviated DAC DR PCAQM abbreviation for Dynamic Range measurement DSP digital signal processing DUT device under test dynamic range the difference usually expressed in dB between the highest and lowest amplitude porti
18. Operator division Date Time test started Comments Creative Sound Blaster Measurement Channel A PLAY D A Path PLAY Sample Rate Error PLAY Level Reference FSOW THD N O PLAY level Rev PB Wave slider at PLAY Level Ref PB Master slider at PLAY Level Ref PLAY Level Ref test conditions PLAY THD N PLAY THD N test conditions PLAY Dynamic Range Ju Figure 42 PC Audio Test workspace with the Results Viewer PC Audio Test User s Manual B 65 Chapter 4 Viewing and Reporting Results The Results Viewer 66 The Results Viewer shows the XML results as formatted dynamic HTML Because this is a dynamic HTML display the data do not reside in the HTML document but are read on the fly from the XML results If a test is running while the Results Viewer is open the window is constantly updated with cur rent results as the test progresses Saving Results You can save test results as an XML file and later open the file to print a report The Results Viewer will always show the current results whether from a test just run or from a previously saved results file that has been opened The XML file always contains all of the results from a particular test What you see in the dynamic HTML display of the Results Viewer depends on the HTML template file in use Like any XML file the XML results file can be formatted and filtered to many purposes by means of a style sheet XML compatible applications in cluding the O
19. audio signals Line level is typically in the 0 dBu to 8 dBu range measurement path in PC audio device testing the combination of soft ware routing and processing and hardware signal path that comprise a distinct mode of operation for the device PC Audio Test recognizes seven measure ment paths Play Analog to Analog Loop Mic Analog to Analog Loop Re cord Mic Record Record Play Loop and Digital Loop multitone testing techniques with stimulus signals consisting of more than one sine wave Most multitone techniques use 15 or more sine waves dis tributed across the audio spectrum one third octave a bandwidth of 1 3 octave or a frequency ratio of 1 2599 1 Three successive frequency changes by this ratio result in a total fre quency change of 2 1 one octave Moderately narrow bandpass filters are of ten set at a bandwidth of 1 3 octave frequency response measurement techniques that use spot frequencies such as real time spectrum analysis or multitone tests often use frequencies centered at 1 3 octave distances passband the frequency band of a filter in which signals are essentially unattenuated also the flat response range of a digital converter between the device corner frequencies passband ripple amplitude variations across the passband of a device This term usually refers to the small amplitude ripple seen in ADC and DAC response curves PCAQM Personal Computer Audio Quality Measurements PC D A PCA
20. m The Windows Autorun features should automatically open the installation menu shown in Figure 12 If this does not occur click the Start button on the Windows taskbar Then click Run and type D Setup and then OK where D is the drive letter of the CD ROM drive m On the installation menu click Install APP 2010 Software to install PC Audio test Configuring DCOM DCOM requires that remote users be identified have proper permission etc to control PC Audio test You must properly configure DCOM and secu rity permissions on the client target computer to use PC Audio Test The following steps will guide you in setting up DCOM and the security permissions on the client computer These steps are described for Microsoft Windows XP We do not recommend using Windows 2000 or Windows 98 for remote testing There may be different combinations of permissions and other settings nec essary to properly configure DCOM for PC Audio Test use depending upon the configuration of your host computer and the design of your network PC Audio Test User s Manual 71 Chapter 5 Remote Testing Configuring DCOM Windows XP The technician performing the test must be an administrator for the client computer Go to Control Panel gt User Accounts to view or change this set ting Run dcomcnfg Windows XP provides a DCOM configuration dialog within the Component Services area of the Microsoft Management Console utility You can access th
21. niques This approach provides very fast precise measurements of both fre quency and phase response at the multitone frequencies PC Audio Test User s Manual 53 Chapter 3 Running the Tests RECORD Measurement Path Eca Level Reference lt ADFSLvIA gt lt ADFSLvIB gt 0 dBr A rec 0 dBr Brec Rec mixer Line In Slider position lt LinelnSlider gt RECTHON lt ADTHDA gt lt ADTHDB gt 54 Stimulus signals for the RECORD path For both single tone and multitone RECORD measurements PC Audio Test controls the instrument analog generator providing the appropriate analog stimulus signal for each measurement Level Reference measurement See the Level Reference sidebar on page 38 The RECORD Level Reference measurement is used as the level reference for recording measurements made by PC Audio Test NOTE You must perform this measurement before other RECORD or RECORD PLAY LOOP path measurements To establish the RECORD Level Reference PC Audio Test applies a 997 Hz sine wave to the DUT Line Input sets the DUT record multiplexer Line In slider to the ANALOG LOOP reference setting if available other wise it is set to the center of its range and varies the level of the applied sig nal to locate the level one step below the level that produces 1 THD N in the DUT output This point is considered to be O dBFS See RECORD Level Reference Settings on page 24 This amplitude is set as the instrument
22. relative to the DUT Analog Input Level AES17 specifies the 1 dB stimulus level WHQL PC2001 specifies 3 dB The DUT analog output is analyzed for THD N As an option you can ap ply an analyzer weighting or bandpass filter if a THD N measurement is fil tered it is typically with a bandpass filter WHQL however specifies a weighting filter The filter must be installed and available in your Audio Precision instru ment See Test Settings in Chapter 2 for more information on applying filters to the THD N or Dynamic Range measurements NOTE In accordance with accepted practice for PC sound device measurements PC Audio Test expresses THD N results relative to the PLAY Level Reference rather than to the stimulus tone level Dynamic Range measurement See the Dynamic Range sidebar on page 48 For the ANALOG LOOP Dynamic Range measurement PC Audio Test ap plies a 997 Hz sine wave at a very low level to the Line Input jacks This tone is typically set to 60 dB relative to the DUT Analog Input Level In the PLAY Dynamic Range measurement see page 40 the purpose of the 60 dB signal was to keep the DAC from muting Although there 1s no DAC in the ANALOG LOOP path the 60 dB signal and the analyzer notch filter to remove it is used so that this measurement will be comparable to the PLAY THD N measurement You can also apply an analyzer weighting or bandpass filter to the Dynamic Range measurement if a Dynamic Range me
23. APIB cable length limitations Audio Precision instruments will operate properly using an APIB intercon nection up to 12 m 40 in length This is the length of two standard Audio Precision APIB cables connected end to end Audio and Grounding cable length limitations Audio interconnections are subject to noise and interference pickup and to signal loss through cable reactance The severity of these effects is effected by circuit impedance signal level and environmental considerations To minimize cable losses and noise pickup we recommend that your audio cables do not exceed the 2 m 6 5 length of the cables included with PC Audio Test To be effective the grounding cable must connect the DUT to the instru ment by a very low impedance For a given gauge longer cable lengths pres PC Audio Test User s Manual Software Installation for Remote Testing Chapter 5 Remote Testing ent higher impedances To minimize ground induced hum and noise we recommend that your ground cable does not exceed the 2 m 6 5 length of the cable included with PC Audio Test Software Installation for Remote Testing APP 2010 PC Audio Test and instrument control software must be in stalled on the host computer See Chapter 2 Additionally you must install APP 2010 software on the target computer To do this m Close all applications on the target computer m Insert the APP 2010 PC Audio Test disk into the target computer CD ROM drive
24. Audio Test has given up and you must go to manual override for this path Failure to find the RECORD level setting can be due to varying signal levels signal interruption non standard DUT driver control or extreme nonlinearity in the driver control law PC Audio Test User s Manual 93 Appendix A Troubleshooting Test Messages 94 Mic A D LevelRef Manual Record A D slider and Generator Amplitude Adjust Last Measurement Chan A 0 00 dBFS THD 0 000 Chan B 0 00 dBFS THD 0 000 If Distortion is high and Level low reduce Generator output Adjust Record A D Manual Override slider control for maximum digital level and THD E Caution When Levels are at 0 dBFS Dis tortion readings are inaccurate Take a new measurement The above message appears during the MIC RECORD manual override level setting procedure This dialog reports the current level and distortion and with the control software displays is an aid to DUT control adjustment Click YES to submit a new setting or NO to accept the current setting ERROR Record Input Channel Connections are Reversed Check DUT Connections and Configuration Channel A and Channel B connections for either the DUT inputs or out puts have been switched one for the other ERROR Both channels have signal with only Chan A Input DUT feeds both channels with Monaural input Either by design or in the DUT driver mixer configuration Channel A is connected to b
25. Dynamic Range sidebar on page 48 PC Audio Test User s Manual MIC RECORD Measurement Path Chapter 3 Running the Tests For the MIC RECORD path dynamic range measurement PC Audio Test applies a 997 Hz sine wave at a very low level to the Mic Input jacks This tone 1s typically set 60 dB below the Mic In level The DUT ADC output 1s acquired directly within the PC and analyzed for dynamic range referenced to O dBFS Frequency Response measurement See the Frequency Response sidebar on page 53 For the MIC RECORD Frequency Response measurement PC Audio Test uses a multitone technique An appropriate multitone signal 1s applied to the DUT Mic Input at a nominal level Depending on your configuration settings the may be at O dBr rec 1 dBr rec 3 dBr rec 6 dBr rec or at a level of your choice NOTE You can specify a custom multitone signal for frequency response testing Custom multitone signals can be created using the Audio Precision Multitone Creation utility or by downloading files from the Audio Precision Web site at audioprecision com See Frequency Response Settings on page 26 The multitone signal in the DUT ADC output is acquired directly within the PC and is analyzed using FFT techniques resulting in a graph showing both frequency and phase response Passband Ripple measurement See the Passband Ripple sidebar on page 55 A second multitone and second FFT analysis are automatically performed during t
26. Getting Ready Launching APP 2010 PC Audio Test NOTE You must have a required version of Audio Precision control software installed on the PC to successfully launch PC Audio Test If PC Audio Test cannot detect a correct version of Audio Precision control software on your PC the program will display a warning dialog and will not open Run the Control Software First NOTE When your installation is complete you must run your Audio Precision control software BEFORE you run PC Audio Test for the first time PC Audio Test requires Audio Precision control software to operate and the control software must make certam entries 1n the registry area of Microsoft Windows before PC Audio test can be successfully opened Be sure that the instrument control software has been run at least once before opening PC Au dio Test for the first time After this initialization PC Audio Test can be run at any time If Audio Precision control software has not previously been installed on your computer refer to the documentation included with your Audio Precision instrument particularly the Getting Started manual for the instrument The Getting Started manual will guide you through the necessary steps for proper hardware connection and software installation Opening APP 2010 PC Audio Test Open PC Audio Test from the Start menu by choosing Start gt All Pro grams gt Audio Precision gt PC Audio Test gt PC Audio Test or by clicking gt th
27. Level Reference mea surement The distortion is measured as unweighted THD N total harmonic distortion plus noise across a bandwidth of 10 Hz to 22 kHz This reading PC Audio Test User s Manual MIC ANALOG LOOP Measurement Path Chapter 3 Running the Tests usually differs from the results in the MIC ANALOG LOOP THD N mea surement discussed below due to possible differences in stimulus level and fil tering Mic In Level measurement With the MIC ANALOG LOOP Level Reference set and measured PC Au dio Test measures the instrument generator output level which is the level ap plied to the DUT Line Inputs This measurement is the MIC ANALOG LOOP Line In Level Mic In Slider setting PC Audio Test reads the playback mixer Mic In slider position at MIC ANALOG LOOP Level Reference The position is reported as a step number See the Slider Position sidebar on page 41 Mic Boost Gain measurement The channel gain is measured with Mic Boost both ON and OFF and the difference is reported in dB as the Mic Boost Gain The maximum gain available in the mic channel with Mic Boost ON is re ported in dB as Mic In Gain Maximum Mic Bias measurements Most PC audio devices with a mono Mic input on a 3 5 mm jack provide a bias current to power those microphones that require bias The Mic In jack is wired with the microphone input on the tip connection and the microphone Signal to Noise Ratio SNR Also see the Dynamic Range sidebar o
28. Measurement Path on page 53 for reference PC Audio Test s RECORD Reference Level algorithm attempts to find the correct analog input recording level for the DUT by searching for the genera tor setting and Line In recording slider control level that produces a digital level just below 0 dBFS at less than 1 distortion To locate the optimal level manually first open the DUT Recording mixer and select the analog input control usually the Line In control and set it to maximum In PC Audio Test click Run The following dialog box will open Manual Record A D slider and Generator Amplitude Adjust ES 9 Last Measurement ChanA 3 46dBFS THD 1 787 ChanB 3 46dBFS THD 1 921 If Distortion is high and Level low reduce Ap Generator output Adjust Record A D Manual Override slider control For maximum digital level and THD lt 1 Caution When Levels are at O dBFS Distortion readings are inaccurate Take a new measurement Figure 57 The ANALOG LOOP manual ad justment dialog This dialog tells you the distortion and digital level measured within the DUT by proprietary techniques in PC Audio Test By adjusting the Line In re cording control volume either from the DUT Configuration panel or from the DUT s recording mixer find the maximum level possible that produces less than 1 distortion Monitor the PC Audio Test digital meter and click the Yes button 1n the dialog box to make a new measurement As you r
29. N MIC REC Level Ref Ch B lt lt o lo lo gt gt gt J IJI ninin INDIO Sle Je OI gt icADFSTHDB DMiclnLv m D FSIV Mic yr icLviGenOutRecLine L Rec mixer Mic In slider position MIC REC Level Ref A D Level Reference test conditions S S ull Scale Input Volt Mic In FSIV 0 dBr eo JAE 5 O a 3 pe O E e J gt O e rm D SEH O gt O A m O gt E E N G O N Mic Supply Current MIC REC THD N test level Ch A MIC REC THD N test level Ch B MIC REC THD N test conditions MIC REC Dynamic Range Ch A MIC REC Dynamic Range Ch B MIC REC Dynamic Range test level Ch A MIC REC Dynamic Range test level Ch B MIC REC Dynamic Range test conditions MIC REC Max Pos Phase Error MIC REC Frequency Response Frequencies Dbl array Dbl array Dbl array MIC REC Frequency vs Relative Phase D MIC REC Frequency Response test conditions no MIC REC Frequency Response Limit imi no MIC REC Passband Ripple Frequencies no MIC REC Passband RippleCh A bl array no MIC REC Passband RippleCh B MIC REC Passband Ripple Limit MIC REC Passband Ripple test conditions bl array D Dbl array imi Str no d tr Mic Boost Gain Maximum Mic In Gain Mic Supply Voltage MIC REC THD N Ch A MIC REC THD N Ch B MIC REC Max Neg Phase Error MIC REC Frequency Response Ch A MIC REC Frequency Response Ch B S O gt
30. Test Settings in Chapter 2 for more information on applying filters to the Dynamic Range and SNR measurements NOTE Due to the absence of a notch filter in the SNR measurement the results may vary slightly from the Dynamic Range results Frequency Response measurement See the Frequency Response sidebar on page 53 For the ANALOG LOOP Frequency Response measurement PC Audio Test uses a multitone technique PC Audio Test causes your Audio Precision instrument analog generator to output an appropriate multitone file for your test NOTE You can specify a custom multitone file for frequency response testing Custom multitone files can be created using the Audio Precision Multitone Creation utility or by downloading files from the Audio Precision Web site at audioprecision com See Frequency Response Settings on page 26 The multitone in the DUT analog output signal is analyzed in your instru ment using FFT techniques resulting in a graph showing both frequency and phase response Crosstalk measurement The Crosstalk measurement is unique to the ANALOG LOOP path For the ANALOG LOOP Crosstalk measurement PC Audio Test applies a 10 kHz sine wave at reference level first on Channel A then on Channel B During each period of stimulus the output of the opposite channel is measured through a 10 kHz one third octave bandpass filter to determine the level of channel to channel crosstalk or bleed through occurring in the DUT Crosst
31. WHQL PC2001 specifies 3 dB The DUT analog output is analyzed for THD N As an option you can ap ply an analyzer weighting or bandpass filter if a THD N measurement is fil tered it is typically with a bandpass filter WHQL however specifies a weighting filter The filter must be installed and available in your Audio Precision instru ment See Test Settings in Chapter 2 for more information on applying filters to the THD N measurements PC Audio Test User s Manual MIC ANALOG LOOP Measurement Path Chapter 3 Running the Tests NOTE In accordance with accepted practice for PC sound device measurements PC Audio Test expresses THD N results relative to the PLAY Level Reference rather than to the stimulus tone level Dynamic Range measurement See the Dynamic Range sidebar on page 48 For the MIC ANALOG LOOP Dynamic Range measurement PC Audio Test applies a 997 Hz sine wave at a very low level to the Line Input jacks This tone is typically set to 60 dB relative to the DUT Analog Input Level In the PLAY Dynamic Range measurement see page 40 the purpose of the 60 dB signal was to keep the DAC from muting Although there 1s no DAC in the ANALOG LOOP path the 60 dB signal and the analyzer notch filter to remove it are used so that this measurement will be comparable to the PLAY THD N measurement You can also apply a weighting or bandpass filter to the Dynamic Range measurement The filter must be available
32. a 110 Switcher assignment 19 T Test Explorer a oaoa a ora 34 Test failure oa a a a a a a a a 36 79 Sb espais cano 27 Test messages 85 PC Audio Test User s Manual Test settings ssw bw Baa pes sda dd ee 22 Test status indicators 36 1 lt A 33 Tests running e is ic ai a a o 36 THD N cc 44 See Distortion THD N settings ss same ds rd eS eR ee 24 Toslink connectors 84 109 U Unbalanced connectors 105 Unity gainmode 24 Unity gainsetting 42 User information 0 28 V Volume controls See Sliders W Windows XP DCOM configuration 72 Word length setting 29 XLR connectors ss aoaaa dd de es 108 AAA 122 XML tagS 6 0 0 ir dor a E Dw 33 97 PC Audio Test Users Manual 125 126 PC Audio Test User s Manual
33. a dear 24 Dynamic Range Settings 25 Frequency Response settings a aoa a a a a a a a 0 26 FEDO amp Aaa rada eS Bene Re ee EG 21 User Information se lis erario 27 Connecting the Hardware 2 2 eee ee ee ee 29 Typical PC audio device Inputs and Outputs 29 PC Audio Cable Set ee 30 Audi Cables 2442 c 8 2 e e 4 BE Setauaeeoauade 31 Mic Bias Cable correccion 31 Ground Cable 2 2 32 Chapter 3 Running the Tests 0 00 0 eee ee ee eee 33 Introduction lt lt xe ek x eb bee eee aaa RCE eG 33 XML tag notation in this chapter 33 The Test Explorer cu de a as Gm SERS GS ES 34 The Measurement Paths 0 0000 2 ee eae 39 Running the Tests ps ELE dE a 36 Test FallureS sc eme sena be eeu ee REA SEE REA 36 PLAY Measurement Path 0 0 00 50 2 eee 37 Introduction to PLAY PC D ADDAN cuore ds rada a eee oe de Dad 37 Stimulus signals for the PLAY path af Level Reference measurement Do this FIRST 2 37 Do PLAY Level Reference FIRST 39 sample Rate Error 2 6 6 db ee wee eel a a a mA 39 THD N at PLAY Level Reference 39 Playback Mixer Wave slider position 39 Playback Mixer Master Volume slider position 39 THD N measurement e o 40 Dynamic Range measurement
34. computer m The Audio Precision instrument must be connected to the host computer via APIB m The host computer must be a node on a well formed Microsoft Windows network PC Audio Test User s Manual 69 Chapter 5 Remote Testing Requirements 70 The Target Computer m APP 2010 PC Audio Test must be installed on the target computer m The target computer must be a node available to the host computer on the Microsoft Windows network m Authentication level controlling computer location security permissions and user identity must be properly set in the DCOM Config dialog NOTE It is beyond the scope of this manual to discuss in any detail the configuration of a Microsoft Windows network or of DCOM Online Help is available within the Microsoft Management Console window which must be opened to access DCOM configuration and much information is available from Microsoft and others in commercial technical publications and on the Web The DUT m The DUT must be installed in the target computer m The DUT must have audio and grounding connections to the Audio Precision instrument Equipment Location for Remote Testing There are practical cable length limitations both to the Audio Precision in strument control cable the APIB cable and to the audio and grounding cables connected between the instrument and the DUT These considerations place a limit on the maximum distance between the local computer and the target com puter
35. devices The tip sleeve TS version has two conductors and is used for single chan nel or mono unbalanced connections The tip is connected to the signal high and the sleeve is connected to the signal low ground Many PC sound device microphone Mic inputs are monaural and use this connector The tip ring sleeve TRS version has three conductors and is ordinarily used as a dual channel stereo unbalanced connection In this configuration the tip is usually connected to the left channel signal high the ring is con nected to the right channel signal high and the sleeve is a common signal low at ground potential With three conductors a 3 5 mm TRS connector can also be used as a sin gle channel mono balanced connection but this 1s unusual a phone plugs and jacks Ring Signal High Tip Right Sleeve Sleeve Tip Sianal High Signal Low EN Signal High Left i RO Ground TS Tip Sleeve TRS Tip Ring Sleeve Mono Plug Stereo Plug Figure 59 phone TS and TRS connectors 4 phone connectors like 3 5 mm plugs and jacks come in tip sleeve TS and tip ring sleeve TRS versions 106 PC Audio Test User s Manual RCA or phono plugs and jacks Appendix C Connector Designations The tip sleeve TS version has two conductors and is used for single chan nel mono unbalanced connections The tip is connected to the signal high and the sleeve is connected to the signal low ground T
36. in this dialog See page 72 for instructions for viewing or changing the default setting On the Location tab select Run application on this computer and be sure that the other options are not checked On the Security tab for PC Audio Test User s Manual 73 Chapter 5 Remote Testing Configuring DCOM udio Precision u es undserver Prope s General Location Security Endpoints Identity The following settings allow DCOM to locate the corect computer for this application If you make more than one selection then DCOM uses the first applicable one Client applications may overide your selections Run application on the computer where the data is located IV Run application on this computer I Run application on the following computer Figure 48 Audio Precision PC Audio Test SoundServer Properties dialog box Location tab m Launch Permissions select Customize and click the Edit button If the host computer s name is not available click Add and enter the name In the Permissions box click Allow Launch Permissions C Use Default Customize r Access Permissions Use Default Customize r Configuration Permissions C Use Default Customize Figure 49 Audio Precision PC Audio Test SoundServer Properties dialog box Security tab m Access Permissions select Customize and click the Edit button If the host computer s name 1s
37. kHz AES17 filter The second 24 PC Audio Test User s Manual Test Settings Chapter 2 Getting Ready field in the THD N settings area allows you to select a different filter or no filter m your Audio Precision instrument for THD N measurements NOTE Most of the filters are optional hardware filters marked with an asterisk in the drop down list Any filter you choose that is marked with an asterisk must be physically installed in the Audio Precision instrument for filter functionality If you select a filter that is not installed in the instrument an error message from the control software states An internal error occurred Value is over list item J max Dynamic Range Settings Dynamic Range Stimulus Level Filters See the Dynamic Range sidebar on page 48 60 dB Below Reference Level 20kHz AES17 E None 22k 20kHz AES17 20kHz a meighting Full BY CCIR 468 3 Full Bw CCIR 2k Dolby ARM Full BY 20k wi A weighting 20k wi CCIR 468 20k wi CCIR 2k Dolby ARM 20kHz Brickwall Full Bv Figure 25 Test Settings dynamic range set tings The dynamic range measurement applies a very low level 997 Hz signal to the DUT to prevent the converter from muting during noise measurements By default the level of this signal is set at 60 dBFS dBr Some measurements may require other levels for the mute defeat tone You can enter a value of your choice in the Dynamic Range St
38. measure ment The distortion is measured as unweighted THD N total harmonic dis tortion plus noise across a bandwidth of 10 Hz to 22 kHz This reading usually differs from the results in the ANALOG LOOP THD N measurement discussed below due to possible differences in stimulus level and filtering o a Line Line In Level measurement With the ANALOG LOOP Level Reference set and measured PC Audio lt AAInLvirA gt a lt AAInLvIB gt Test measures the instrument generator output level which is the level applied to the DUT Line Inputs This measurement is the ANALOG LOOP Line In Level Line In Slider setting PB mixer Line In Slider position PC Audio Test reads the playback mixer Line In slider position at lt LineMonOutSlider gt ANALOG LOOP Level Reference The position is reported as a step number See the Slider Position sidebar on page 41 Distortion THD N There are many ways to distort an audio signal but in this sidebar we will only consider harmonic distortion Harmonic distortion occurs under condi tions of non linearity usually due to overload in a device and is character ized by the presence in the output signal of integer multiples of the stimulus frequency or harmonics These harmonics can be primarily even harmonics x2 x4 etc primarily odd harmonics x3 x5 etc or a mixture of both The amplitudes of the harmonics generally decrease with frequency For many purposes the ampli
39. message indicates a regulation error within the control software when PC Audio Test is adjusting analog level reference This is usually due to unstable or varying signal level or frequency or possibly noise or interference in the DUT Caution Levels are out of balance by 0 0 dB Check DUT Pan Balance The above message may appear at any point in a test It indicates a Channel A to Channel B level imbalance due to Pan or Balance control settings in the DUT software driver mixer D A LevelRef Manual Play D A slider Adjust Last Measurement Chan A 0 00dBV THD 80 00 Chan B 0 00 dBV THD 0 00 Adjust Play D A Manual Override slider control for maximum level and THD lt 1 Take a new measurement The above message appears during the PLAY manual override level setting procedure This dialog reports the current level and distortion and with the control software displays is an aid to DUT control adjustment Click YES to submit a new setting or NO to accept the current setting PC Audio Test User s Manual 87 Appendix A Troubleshooting Test Messages ADJUSTMENT FAILED Low Output level and THD N gt 1 Master and WAV slider at maximum Probable No Signal condition Check Connections and DUT Properties Configuration This message usually means there is no signal which usually points to a connection problem a DUT or instrument configuration problem or an extra DUT software driver mixer control
40. remote computer that each report the same manufacturer and model name to the operating system the matching sound devices will share the same PC Audio Test configuration files Properties Viewing or Editing a DUT Configuration To view or edit a DUT configuration select a configuration branch and click the View the selected configuration button on the DUT toolbar or dou ble click the configuration branch or right click in the DUT Explorer and choose Properties from the menu The selected DUT Configuration panel will open PC Audio Test User s Manual 17 Chapter 2 Getting Ready DUT Selection and Configuration The DUT Configuration panel DUT Line In Mic In Digital Out Digital In Master Play D A Input 4 4 Mic Boost Digital Out Digital In Comments r Connection Assignments Line or Spkr Out to ENcUnbal v 1 amp 2 DUT Driver Software Record 4 D Microphone 4 4 Audio Precision Hardware Instrument Switcher from Unbal Float 1 8 2 from Bal Float 1 amp 2 to BNC unbal M 1 amp 2 From BNC unbal 1 amp 2 Mixer Assignment Manual Override volume Control O lo 4 Wave v O tren y O meve e O 4 0 E 0 0 E 150 none wi Figure 15 The DUT Configuration panel Assigning Connections DUT Line In Mic In Digital Out Digital In Connection Assignments Ground Check
41. s Manual Quick Tour Chapter 1 Introduction Reports q PC Audio Device Ato E ceri ue rehensive Test Re PC Audio Device j Comprehensive Test Report on Figure 10 Typical HTML Reports PC Audio Test results are stored as XML text which can easily be con verted into many different report formats HTML templates are included to get you started generating reports You can write your own HTML templates or import the XML results data into compatible spreadsheet database or word processor applications Remote PC Device Testing PC Audio Test can be installed on a host computer and can acquire a full set of measurements from a DUT installed on a remote client or target computer The host computer must be connected to the Audio Precision instrument performing the measurements and have both PC Audio Test and the instrument control software installed The target computer must have PC Audio Test installed be connected to the host computer via a network connection and must be properly configured for DCOM remote operation DCOM is a distributed computing feature included with Microsoft Windows 2000 and Windows XP We do not recommend using Windows 98 for remote testing See Chapter 5 for more information about making remote measurements from a target computer using DCOM PC Audio Test User s Manual 11 Chapter 1 Introduction Quick Tour Cables Figure 11 PC Audio Test Cable Set Several cables are incl
42. standard mixer controls such as Front or Back in a surround capable DUT that may affect PLAY lev els Set such controls that are in the signal path to maximum and set those controlling other signals that may be mixed with the PLAY signal to minimum Manual PLAY level control setting See PLAY Measurement Path on page 37 for reference PC Audio Test s PLAY Reference Level algorithm attempts to find the cor rect playback operating level for the DUT by searching for the maximum PLAY level that produces less than 1 distortion THD N at the DUT Line or Speaker output To locate the optimal level manually first open the DUT Playback mixer and set the Master Volume and the PLAY volume usually the Wave control to their maximum In PC Audio Test click Run The following dialog box will open Manual Play D A slider Adjust 2 Last Measurement Na j Chan4 amp 7 04dBY THD 0 01 ChanB 7 04 dBv THD 0 01 Adjust Play D A Manual Override slider control For maximum level and THD lt 1 Take a new measurement Figure 55 The PLAY manual adjustment di alog This dialog tells you the measured level and distortion at the DUT output By adjusting the Wave control volume either from the DUT Configuration panel or from the DUT s playback mixer find the maximum level possible that produces less than 1 distortion Monitor the control software readings and click the Yes button in the dialog box to make a new meas
43. that is not enabled ADJUSTMENT FAILED Low Output level WAV slider at maximum Master slider is manually set Check setting The message above usually means there is no signal which points to a con nection problem a DUT or instrument configuration problem or an extra DUT software driver control that is not enabled This message appears only when the Master slider control has been set to manual override so check the Master setting ADJUSTMENT FAILED WAV slider is at minimum and THD N gt 1 This is unusual but 1t can happen The DUT D A path is overloading when a full level 0 dBFS digital signal is played ADJUSTMENT FAILED 20 adjustment loops done Unity Gain slider setting not found On the DUT Properties Configuration Record D A check Manual Override Set slider for maximum level and THD lt 1 After 20 tries to find the correct PLAY level setting PC Audio Test has given up and you must go to manual override for this path Failure to find the PLAY level setting can be due to varying signal levels signal interruption 88 PC Audio Test User s Manual Test Messages Appendix A Troubleshooting non standard DUT driver control or extreme nonlinearity in the driver control law ADJUSTMENT FAILED 20 single step adjustment loops done Unity Gain slider setting not found On the DUT Properties Configuration Record D A check Manual Override Set slider for maximum level and THD lt 1
44. that may be generated in the device will be of a level well below the residual noise level and therefore un measurable This technique provides a true dynamic range value for the device in an unmuted condition A stimulus tone of 997 Hz at 60 dBr rec 60 dBFS in a normally refer enced test is specified for PC audio devices of 16 bit resolution For consistency PC Audio Test measurements that do not include a DAC RECORD and the ANALOG LOOP paths use the same 60 dBr tone in the stimulus signal and notch filter in the analysis Stimulus signals for the MIC ANALOG LOOP path For both single tone and multitone MIC ANALOG LOOP measurements PC Audio Test controls the instrument analog generator providing the appro priate analog stimulus signal for each measurement Level Reference measurement The MIC ANALOG LOOP Level Reference is the output voltage measured at the analog outputs when the MIC ANALOG LOOP path Level Reference criteria are satisfied See the Level Reference sidebar on page 38 PC Audio Test searches for the signal that can be applied to the Mic In jack while producing less than 1 THD N at the Output jacks for any mixer Mic In volume slider setting The voltage at the Line Out jack is measured and re ported as the MIC ANALOG LOOP Level Reference THD N at MIC ANALOG LOOP Level Reference After the Level Reference has been set the same 997 Hz tone is analyzed for its distortion as part of the MIC ANALOG LOOP
45. wired for mic bias current See Mic Bias measurements below PC Audio Test User s Manual 47 Chapter 3 Running the Tests MIC ANALOG LOOP Measurement Path MIC LOOP Level Reference lt AAMicFSLvIA gt lt AAMicFSLvIB gt MIC LOOP THD N Level Reference lt AAMicFSTHDA gt lt AAMicFSTHDB gt 48 Dynamic Range A dynamic range measurement for a PC audio device is essentially a sig nal to noise ratio measurement it provides the ratio between the maximum level possible in the device to the level of the residual noise of the device Like a signal to noise measurement the device output is often filtered with bandpass or weighting filters to provide meaningful or comparable results Any filtering applied must be acknowledged with the results There is a key difference in performing a dynamic range measurement on a device that uses a DAC in its processing most DACs mute their output when the digital signal falls to a very low level This provides an unrealistically low level of residual noise since the output is not the noise of the system but the output of a muted DAC This noise measurement with the DAC muted is called the Idle Channel Noise measurement To prevent this muting dynamic range tests for PC audio devices use a low level stimulus tone to keep the DAC in an unmuted condition This tone is removed before measurement using a notch filter and is set to a low enough value that any components of harmonic distortion
46. with AES3 and 60958 S PDIF protocols and data handling accuracy The full DIGITAL LOOP measurement path requires that the DUT has both DIGITAL LOOP a digital input and digital output The digital stimulus signal is applied to the Sample Rate digital input routed through the recording mixer and then through the play lt DDOutSR gt back mixer to the digital output Not all PC audio devices have digital inputs or outputs or both PC Audio Test can perform some partial loop path measurements for PC audio devices that have only a digital input or a digital output but not both Interface Characterization measurements For DUTs that have a digital output PC Audio Test measures the DUT Dig ital Output impedance Z and signal voltage peak to peak The output sample rate is measured DIGITAL LOOP Output Voltage lt DDOutV gt For DUTs that have a digital input PC Audio Test measures the Digital In put impedance PC Audio Test User s Manual 63 Chapter 3 Running the Tests DIGITAL LOOP Measurement Path Protocol Verification E LOOP For DUTS that have a digital output the output interface signal metadata QEU protocol is evaluated providing a Status Bits summary a verification of cor lt DDOutStatBit gt rect Error Flag display and a verification of the output resolution and output sample rate indicator bits and the state of the Device Type indicating SRC and Valid bits 64 PC Audio Test User s Man
47. with three conductors an internal twisted pair of wires one carrying signal or HIGH the other carrying sig nal or LOW These are surrounded by a third conductor in the form of a braided or foil shield which is connected to the common or ground terminal at one or both ends of the cable Used with properly engineered equipment balanced lines are superior in per formance to unbalanced connections yielding better reyection of common mode interference caused by electrostatic and electromagnetic fields Addi tionally since the audio in a balanced circuit is isolated from the ground con ductor ground current induced noise is much more easily dealt with Also called a symmetrical line See ground unbalanced bandpass filter a filter that passes a specific frequency band called the passband essentially without attenuation while attenuating frequencies both below and above the specified band bit depth see word length bits of resolution the number of bits of the binary word by which signals are represented in a digital recording or transmission system Each bit adds ap proximately 6 dB to the theoretical dynamic range available Thus a 16 bit digital system is capable of approximately 96 dB dynamic range etc bus in electricity and electronics a conductor common to three or more circuits In computers the data bus is a set of conductors that carry common data between three or more subunits of the computer cl
48. 60 Stimulus signals for the RECORD PLAY LOOP path 60 THD N measurement 2 2 A 60 Dynamic Range measurement 0 05008 ee ae 61 Frequency Response measurement 0204 61 DIGITAL LOOP Measurement Path 63 Introduction to DIGITAL LOOP Measurement Path D D path secs ee ede ete ee ke eee Ras 63 Interface Characterization measurements 63 Protocol Verification lt 2224tis aeae dee Bw Ow Se Se eS 64 Chapter 4 Viewing and Reporting Results 65 The Results Viewer 2 a 65 Saving Results gt bo ea ara hrs Ea RE KS 66 HTML templates os ck awe ee eu be bee ee eee SE SES 66 Printing Reports ria eee hee eh eee Ee ee a 67 Chapter 5 Remote Testing o 69 IMHocuciOA lt lt 2 urea ora a eee 69 Requirements eses be bee eae Ee eRe eS we a 69 The Host Computer a eee ee 69 The Target Computer e 70 The DUT pe ag ea 8 Bee 5 aaa 70 Equipment Location for Remote Testing 70 APIB cable length limitations 04 70 Audio and Grounding cable length limitations 70 Software Installation for Remote Testing 71 Configuring DCOM oaaae a 71 WINCOWS A e ee oboe ake eee eRe ea ee ee Boe bee dg 72 RUN COMentO e a ssie eee e a A So 72 Connecting the Hardware 0 000 eee eee 75 Remote Testing with DCOM
49. AES3 interface is partially compatible with the digital signal carried on the S PDIF interface AES17 1998 A standard providing methods for specifying and verifying the performance of digital audio equipment analog audio analog signal a representation of an audio signal as a con tinuously variable quantity An analog audio signal is usually an electrical voltage varying in analogy to the sound waves it represents analog to digital converter a device for converting an analog input sig nal into a series of digital values representing the instantaneous amplitude of the signal at regular sampling intervals Abbreviated ADC See digital record ing or processing PC Audio Test User s Manual 113 Appendix D Glossary analog to digital abbreviated A to D A D A D and so on See digital recording or processing and analog to digital converter AP2700 the Audio Precision control software for the 2700 series of audio test and measurement instruments APWIN the Audio Precision control software for the System One Sys tem Two and System Two Cascade lines of audio test and measurement instru ments ATS the Audio Precision control software for ATS 2 audio test and mea surement instruments balanced a term referring to an audio transmission line in which the sig nal is applied differentially between two conductors each of which has equal impedances to a common reference or ground A balanced line is usually constructed
50. APIs 78 A utility called MixApp exe 1s included with PC Audio Test that can be used to view the entire set of mixer parameters sources destinations controls defined by the PC audio device under test Special Run Modes for PC Audio Test In attempting to perform tests on devices that do not use the Windows Mixer API or use it in non standard ways PC Audio Test may encounter mut ing routing effect or volume controls that are not accessible and some or all of the tests may fail or report results that do not represent the best performance of the device under test PC Audio Test has two special run modes that can be used when problems arise 1n testing non standard PC audio devices These modes are accessed by launching the PC Audio Test using a command line with an argument switch to set the mode You can launch PC Audio Test with a command line by using the Windows Run dialog box as described below or you can make a short cut that includes the switch argument in the target string These two run modes modify the way that PC Audio Test controls the DUT driver mixer controls The tests become less automated giving you the oppor tunity to make settings optimized to the DUT design However PC Audio Test is not able to optimize levels effectively in these special run modes and it be comes the operator s responsibility to choose routing muting and level set tings that produce correct optimum test results AutoOff T
51. B gt Frequency R P LOOP Response lt ADDAResponse gt PC Audio Test User s Manual 61 Chapter 3 Running the Tests RECORD PLAY LOOP Measurement Path NOTE You can specify a custom multitone file for frequency response testing Custom multitone files can be created using the Audio Precision Multitone Creation utility or by downloading files from the Audio Precision Web site at audioprecision com See Frequency Response Settings on age 26 EE LOOP pag RSE P The multitone in the DUT analog output signal is analyzed in your Audio Precision instrument using FFT techniques resulting in a graph showing both lt ADDAResponse gt frequency and phase response 62 PC Audio Test User s Manual DIGITAL LOOP Measurement Path Chapter 3 Running the Tests DIGITAL LOOP Measurement Path DIGITAL INTERFACE lt RECEIVER RECORDING RECORDING DIGITAL IN POSSIBLE MUX DIGITAL IN SAMPLE RATE MULTIPLEXER SLIDER CONVERTER R DIGITAL gt PLAYBACK ___ INTERFACE gt 0 i MAES TRANSMITTER PLAYBACK PLAYBACK DIGITAL OUT DIGITAL IN MASTER Or SLIDER NONE SLIDER Figure 41 DIGITAL LOOP path block diagram Introduction to DIGITAL LOOP Measurement Path D D path Unlike the other measurement paths DIGITAL LOOP does not test the au dio capabilities of the DUT Instead this path evaluates the digital interface characteristics measuring interface electrical parameters compliance
52. Each test result has an XML tag or collection name associated with it Result Name When re formatting existing reports or creating new ones you will need to know the tag associated with the results you report In this chapter boxes in lt ResultTag gt the margins will identify both the result description blue box and the XML tag white box for that result Tables m Appendix B list all results tags PC Audio Test User s Manual 33 Chapter 3 Running the Tests The Test Explorer The Test Explorer TestExplorer ax ye Untitled Testi AG Test Settings AG Test ID I BX PLAY D 4 Path o RJE Level Reference DE THD N BE Dynamic Range i x _ Frequency Response BED Passband Ripple I N ANALOG LOOP A A Path MIC ANALOG LOOP 4 4 Path REC A D Path MIC REC AJD Path REC PLAY LOOP 4 D PC D 4 Path ai DIGITAL LOOP D O Path BIZ Output BJ Input BJ Data validity Bittest D E E E E E Figure 33 The Test Explorer The Test Explorer Figure 33 displays the measurement paths and measure ments in a hierarchical tree structure You can select or deselect a particular measurement or entire measurement paths The highest level of the tree is the test identified by the test name Double clicking on this branch will expand or collapse the tree display A new test settings file is named Untitled Test 1 From the File menu you can save a new test settings file with an identifying name by cho
53. L templates 66 SOI apso reed 67 Identity property for DCOM 75 ECO O ew ears teed eee ee AA 121 Inputs and Outputs PC audio device 29 Installation Local testing host computer 13 Remote testing target computer 71 Instrument connections 18 J JACKS 24 24 2 2 ALA e a bee OES 106 107 L Level Reference 38 Level reference failures 80 Location property forDCOM 13 M Male connectors 24 4 105 Manual control setting ANALOG LOOP 82 Manual control setting PLAY 81 Manual control setting RECORD 83 Measurement paths 8 35 MIC ANALOG LOOP measurement path 47 MIC ANALOG LOOP path results 100 Mic Bias cable 12 30 31 47 Mic Boost control assignment 21 Mic boost switch 24 MIC RECORD measurement path 57 MIC RECORD path results 102 Microsoft Management Console 72 O Optical connectors 109 P Passband Ripple 55 Paths See Measurement paths PC Audio Test i da ae aw a eae ee a 3 system diagram 2 0808 3 POZOI ace enea eee ees dias 122 PCAQM See Personal Computer Audio Quality Measurements PC D A See PLAY measurement path 124 Personal Computer Audio Quality Measurements 34 122 PLAY level reference
54. PB Master slider at PLAY Level Ref PLAY Level Ref test conditions PLAY THD N PLAY THD N test conditions PLAY Dynamic Range ee ea A Figure 4 PC Audio Test workspace PC Audio Test launches with the Test Explorer and the DUT Explorer win dows open and with the Results viewer in the workspace The real time digi tal audio meter is displayed on the right Device Under Test DUT PC Audio Test will query the PC and the remote target PC if connected and properly configured to determine the sound device s installed These in stalled sound devices are listed in the DUT Device Under Test Explorer win dow with a sound card icon Each sound device listed has one or more configurations attached to it designated by a wrench icon PC Audio Test User s Manual Quick Tour Chapter 1 Introduction DUT Explorer a X dX or El My Computer Creative Sound Blaster PCI Creative Sound Blaster PCI 1 P Creative Sound Blaster PCI 2 S Creative Sound Blaster PCI 3 SP SoundMas Digital Audio gP SoundMax Digital Audio 1 Figure 5 The DUT Explorer panel Choose the sound device and configuration you would like to test by setting the configuration to Active Set a configuration to Active by selecting the con figuration then clicking the star icon in the DUT Explorer toolbar When a configuration and sound device are set to Active they are displayed in BOLD type Creative Sound Bl
55. QM PC2001 abbreviation for Personal Computer Analog Digital measurement path Commonly referred to in PC Audio Test as the PLAY measurement path pulse code modulation a form of data transmission in which amplitude samples of an analog signal are represented by digital numbers Abbreviated PCM Almost all digital audio schemes use PCM resolution the smallest change in a measured parameter to which a mea surement instrument can respond The resolution of a PCM digital audio sys PC Audio Test User s Manual 117 Appendix D Glossary 118 tem corresponds to 1ts digital word length digital systems for example can be described as having 16 bits of resolution rms see root mean square root mean square the preferred form of ac signal detection that measures amplitude in terms of its equivalent power content regardless of signal waveshape Abbreviated rms sample frequency sample rate the frequency at which the signal is sam pled in a digital system The sample rate must exceed twice the highest analog frequency to be converted Commonly used sample rates are 48 kHz 44 1 kHz and 32 kHz signal to noise ratio the difference 1n level between a reference output signal typically at the normal or maximum operating level of the device and the device output with no signal applied Signal to noise ratio is normally stated in dB The device input conditions for the noise measurement must be specified such as inpu
56. UT for this session from this window Testing a remote sound device across a network connection is discussed in detail in Chapter 5 Viewing the Device Properties Device Properties Mixer Mame Creative Sound Blaster PCI Manufacturer ID Product ID Figure 14 Viewing the Device Properties PC Audio Test can read certain device properties for the DUTs installed on your system Double click a DUT branch to view the Device Properties win dow for that DUT PC Audio Test User s Manual DUT Selection and Configuration Chapter 2 Getting Ready Selecting a DUT Configuration Each DUT listed m the DUT Explorer has one or more configurations asso ciated with it A DUT configuration identified by a wrench icon defines the settings used to enable correct driver control and audio signal routing for the DUT A default configuration is assigned to each DUT Configurations can be ed ited named and saved as cfg files Saved files can be opened and assigned to the selected DUT You may have many configurations for each DUT but only one configura Jo tion can be active at any time To select a DUT and set a configuration to ac tive choose a configuration branch and click the star button on the DUT Set Active toolbar or right click in the DUT Explorer and choose Set Active from the E menu nem Save HR Delete NOTE If you have a sound device on the local computer and a second sound device on the
57. aise the level there will usually be a threshold at which the distortion increases greatly set the level just below this point This level is usually very close to O dBFS If the lowest setting of Line In still produces more than 1 distortion and level is high set the Line In control at lowest active setting Adjust the instru ment Analog Generator level downward a Bar Graph control is available m the control software display to set and view the generator level until you find the find the maximum level possible that produces less than 1 distortion Then continue with your test PC Audio Test User s Manual 83 Appendix A Troubleshooting Test Failures NOTE Many DUTs employ audio compression or limiting circuits between the Line In jack and the DUT ADC circuits In may cases these circuits may make it impossible to approach or equal O dBFS or they may induce high distortion in the signal several dB below O dBFS 84 PC Audio Test User s Manual Test Messages Appendix A Troubleshooting Test Messages In the course of operating PC Audio Test you may see dialog boxes report ing test status caution and error messages These may be generated by PC Au dio Test by the instrument control software or by the computer operating system The messages created by PC Audio Test follow with explanations General An internal error has occured Value is over list item max The above message is issued by the control soft
58. al Float miez w E E E 3 O Frequency Response L L E crosstalk Digital Out to BNC unbal w 1 amp 2 x RO mic ANAL OG LOOP A A P Digital In From BNC unbal iv 1 amp 2 iv C Mute all C Mute DUT Explorer a x DUT Driver Software Done Testing PLAY D A Path Level Reference For Help press F1 Figure 54 Screen display for a typical Manual Override adjustment setting session Creative Sound Blaster PCI PC Audio Test User s Manual Test Failures Appendix A Troubleshooting Figure 54 shows a typical user interface for manual override setting Notice that the Windows Volume Control Mixer is visible and that PC Audio Test is running in a small window so that the control software displays can be viewed To enable manual setting for a control check the manual override box for that control on the DUT Configuration panel In most cases you will want to open the DUT mixer window as well The default Windows mixer is called Volume Control and is available at Start gt Programs gt Accessories gt Enter tainment gt Volume Control Proprietary mixers will be available from other locations Once the Manual Override checkbox is checked you can set the level of that control from a mixer panel or by entering a number between and the maximum step number which varies greatly with DUT design in the Manual Override control field Be sure there to check for non
59. alk is expressed as the ratio of the measured crosstalk level to the stimulus level in decibels PC Audio Test User s Manual MIC ANALOG LOOP Measurement Path Chapter 3 Running the Tests MIC ANALOG LOOP Measurement Path MIC BOOST lt O MIC IN MIXER PLAYBACK PLAYBACK aes MIC IN MASTER or SLIDER VOLUME SLIDER Figure 36 MIC ANALOG LOOP path block diagram Introduction to MIC ANALOG LOOP A A mic path MIC ANALOG LOOP is an alternate ANALOG LOOP path for PC audio devices that have no line inputs such as those found on most notebook PC im plementations The measurements are similar to those in ANALOG LOOP with the addition of a few Mic In specific measurements In MIC ANALOG LOOP the PC audio device buffers and sets the level of the analog audio presented at the Mic input and then routes the signal through the playback mixer and to the device analog outputs Mic Boost gain and mi crophone bias voltage and current are measured Using the Mic Bias cable Most PC audio devices with a 3 5 mm Mic In jack provide a monaural sin gle channel microphone input with a bias current available to power electret condenser microphones The Mic Bias cable provided with PC audio test en ables you to test the audio performance and measure the mic bias voltage with out re patching interconnections We recommend you use this cable for MIC ANALOG LOOP testing on PC audio devices fitted with a 3 5 mm mic jack
60. amic Range measurement See the Dynamic Range sidebar on page 48 For the RECORD PLAY LOOP Dynamic Range measurement PC Audio Test applies a 997 Hz sine wave at a very low level to the Line Input jacks This tone is typically set to 60 dB relative to the DUT Analog Input Level The tone is removed by a narrow notch filter in the analyzer before the residue is measured This signal is routed through the DUT ADC and digitally recorded as a tem porary wave file The file is then played and routed through the DUT DAC and to the Line Out jacks The DUT analog output 1s analyzed for Dynamic Range You can also apply an analyzer weighting or bandpass filter to the Dynamic Range measurement if a Dynamic Range measurement is filtered it is typi cally with a weighting filter The filter must be installed and available in your Audio Precision instru ment See Test Settings in Chapter 2 for more information on applying filters to the Dynamic Range measurements Frequency Response measurement See the Frequency Response sidebar on page 53 For the RECORD PLAY LOOP Frequency Response measurement PC Au dio Test uses a multitone technique An appropriate multitone signal is applied to the DUT Line Input at a nominal level Depending on your configuration settings the stimulus level may be at O dBr pec 1 dBr rec 3 dBr rec 6 dBr rec or at a level of your choice R P LOOP Dynamic Range lt ADDADynRngA gt lt ADDADynRng
61. and Measurements 2 00582 ee uae 8 Test Settings ed eee bw ee ee dadas oe EE 9 Test Results e 10 RODOS o ese keeeeea asas sd 11 Remote PC Device Testing eee 11 COD 22444 Pages as sas 12 Chapter 2 Getting Ready a 13 Installing the Software aoao aa 2 2 13 Launching APP 2010 PC Audio Test 15 Run the Control Software First 15 Opening APP 2010 PC Audio Test 0 15 DUT Selection and Configuration a aoa a oa a a a a a a a a 15 The DUT Explorer y oaoa ESSE E 16 Viewing the Device Properties o aoa a a a a a a a 16 Selecting a DUT Configuration oaoa a e e a 17 Viewing or Editing a DUT Configuration 17 The DUT Configuration panel oaoa oaa a a a a 18 Assigning Connections a a a a a a a a 18 Groumma Check ce ss ss sega Peewee eee HIDE RA 19 Assigning Mixer Sliders 2 2 a a 20 PC Audio Test User s Manual Contents Automatic and manual level setting 21 Mic Boost Assignment 4 Gd aK ER EME Se we e wm 21 Test Settings Gcieuswihdewig dee sh bbedseeutass 22 The Test Settings dialog box o o aooaa a a a a 22 Digital Settings oa dara DES DES he E Sa 23 Level Reference Settings 2 0 a a 23 MADENSORMOS s s i aap
62. aster PCI 1 m mx Connection Assignments Audio Precision Hardware DUT Instrument Switcher Line or Spkr Out to BNC Unbal v 1 amp 2 Line In From Unbal Float 1 amp 2 Mic In from Bal Float 1 amp 2 v Digital Out to BNC unbal w 182 Digital In from BNC unbal w 1 amp 2 DUT Driver Software Mixer Assignment Manual Override Master volume Control C a Play D A Wave O jo rut A A E Record A D Mic Volume Microphone 4 4 Mic Boost none v Digital Out none Digital In none v Comments Figure 6 DUT Configuration panel A DUT must be configured for testing Configuration establishes the soft ware mixer assignments for the DUT functions and selects the measurement instrument ports and interface settings PC Audio Test User s Manual 7 Chapter 1 Introduction Quick Tour The default configuration for each DUT combines mixer assignments polled from the sound device driver and typical test settings You can edit the default DUT configuration to match special characteristics of your DUT and the needs of your test Once edited DUT configurations can be named and saved as cfg files For more information see DUT Configuration on page 18 Paths and Measurements Test Explorer a ye Untitled Testi ti Test Settings 3 Test ID Be gt PLAY C A Path BR Level Reference EIM THD N ae EIL Dynamic Range y BJ Frequen
63. asurement is filtered it is typi cally with a weighting filter The filter must be installed and available in your Audio Precision instru ment See Test Settings in Chapter 2 for more information on applying filters to the THD N measurements Signal to Noise Ratio measurement This Signal to Noise Ratio SNR measurement is unique to the ANALOG LOOP paths both Line In and Mic In PC Audio Test User s Manual ANLG LOOP THD N lt AATHDA gt lt AATHDB gt ANLG LOOP Dynamic Range lt AADynRngA gt lt AADynRngB gt JANLG LOOP SNR 45 Chapter 3 Running the Tests ANALOG LOOP Measurement Path lt AASNRA gt lt AASNRB gt Frequency Response ANLG LOOP lt AAResponse gt Frequency vs Phase ANLG LOOP ANLG LOOP Crosstalk lt AAXtIkA B gt lt AAXtIkB A gt 46 It is similar to the ANALOG LOOP Dynamic Range measurement but does not use a low level tone for stimulus or an analyzer notch in measurement In stead the broadband noise at the Line Out jacks is measured and expresses as a ratio to the ANALOG LOOP Level Reference Like the THD N and Dynamic Range measurements you can apply a weighting or bandpass filter to the SNR measurement if an SNR measurement is filtered it is typically with a weighting filter The filter must be available in your Audio Precision instrument The Dy namic Range filter selection is used as the selection for filtering SNR measure ments See
64. at a very low level that prevents the DAC from muting This tone is typically set to 60 dBFS The tone is removed by a narrow notch filter in the analyzer before the residue is measured You can also apply an analyzer weighting or bandpass filter to the Dynamic Range measurement if a Dynamic Range measurement is filtered it 1s typi cally with a weighting filter The filter must be installed and available in your Audio Precision instru ment See Test Settings in Chapter 2 for more information on applying filters to the Dynamic Range measurements PLAY Frequency Frequency Response measurement Response See the Frequency Response sidebar on page 53 lt DAResponse gt PLAY Frequency vs Relative Phase 40 PC Audio Test User s Manual For the PLAY Frequency Response measurement PC Audio Test uses a multitone technique A set of multitone files were installed on the target PC during installation and PC Audio Test plays the appropriate file for your test PLAY Measurement Path Chapter 3 Running the Tests NOTE You can specify a custom multitone file for frequency response testing Custom multitone files can be created using the Audio Precision Multitone Creation utility or by downloading files from the Audio Precision Web site at audioprecision com See Frequency Response Settings on page 26 The multitone in the DUT analog output signal is analyzed in your Audio Precision instrument using FFT techniques result
65. audio applications are the Windows WavelO API and the Windows Mixer API Volume Control Sound Recorder and Windows Media Player all included in a Windows installation are examples of applica tions that control audio using these APIs as is Audio Precision s PC Audio Test The dedicated mixer and control panels included with most sound cards and other PC audio devices are almost always compatible with the Windows WavelO API However many PC audio devices are not fully compatible with the Windows Mixer API Demand for new features often results in designs with controls and capabilities that are not included in the Windows Mixer API and custom software drivers must be included with the audio device to accom modate these non standard controls PC Audio Test cannot access non standard controls and when a PC audio devices has non standard controls in a test path these controls must be manu ally set or disabled The Windows Mixer API The Windows Mixer API makes audio sources SRC and destinations DST available with controls that modify the connecting mixer lines These relationships are displayed graphically in the standard Windows Mixer panel SndVol32 exe The Playback mixer shows the mixer lines and their controls connected to the Speakers destination the Record mixer shows the mixer lines and controls connected to the Wave destination PC Audio Test User s Manual 77 Appendix A Troubleshooting Compatibility with Windows
66. c and Line inputs PC Audio Test will use the selections you have made here Level Reference Settings Level References Play D A O dBFS w O dBr P 4 4 Unity Gain 4 0 0 dBFS Record A D ars PBFS E Mic Boost On 3 0 dBFS 6 0 dBFS THD N Figure 23 Test Settings level reference set tings See the Level Reference sidebar on page 38 There are two key level references settings in PC Audio Test m PLAY D to A level reference PLAY D to A level reference establishes the relationship between a particular digital level the default 1s O dBFS at playback and the corresponding electrical level at the analog Line Out jacks which are normalized as 0 dBrp ay A and B This level is also referred to as FSOV or Full Scale Output Voltage PC Audio Test User s Manual 23 Chapter 2 Getting Ready Test Settings RECORD A to D level reference 0 dBr rec RECORD A to D level reference establishes the electrical level at the FSIV analog input normalized as 0 dBr rsc required to cause a particular digital level the default being 0 dBFS to be recorded This level is also referred to as FSIV or Full Scale Input Voltage Some standards specify and some measurements require other digital level references typically 1 dBFS 3 dBFS or 6 dBFS You can select any of these values or enter a value of your choice in the Level Reference setting field for either the PLAY or RECORD Level Refer
67. chez Clif Personal Computer Audio Quality Measurements PCAQM Crystal Audio Division Cirrus Logic September 1999 www cirrus com PC2001 Hardware and software requirements for PC 2001 audio PC 2001 System Design Guide Chapter 11 Audio Intel Corporation and Microsoft Corporation 2000 www intel com www microsoft com Wayne Jones Michael Wolfe Theodore C Tanner Jr Daniel Dinu Testing Challenges in Personal Computer Audio Devices AES Convention Paper 5814 presented at 114th AES Convention Amsterdam The Nether lands March 2003 www aes org XML http msdn microsoft com library default asp url nhp de fault asp contentid 28000438 http www w3 org XML 122 PC Audio Test User s Manual Ya plugs and jacks 106 3 5mm plugs and jacks 106 SDSS Buy Geet aaGeaw ee eee wa eax 121 A A D PC D A See RECORD PLAY LOOP measurement path AEST sobrar eee Bees ee ee 121 FESO ee ss eae E dE DA E DE ee E Hla 121 ANALOG LOOP manual control setting 82 ANALOG LOOP measurement path 42 ANALOG LOOP path results 99 APP 2010 See PC Audio Test Authorization Level for DCOM 73 Automatic and manual level setting 21 B Balanced connectors 105 Bit depth setting 24k eee es oe ae eS Ed 23 BNC connectors 108 C Cable set o a Gd we wee a Ss 12 30 Component Services See Microsoft Manag
68. cy Response EJ Passband Ripple RJA ANALOG LOOP A A Path MIC ANALOGS LOOP 4 4 Path REC A O Path MIC REC 4 0 Path x RECIPLAY LOOP A D PC D A Path E x DIGITAL LOOP D D Path x a Output EJL Input BEL Data validity Bittest E i E E Figure 7 The Test Explorer panel PC sound devices operate over various signal paths such as PLAY RECORD or ANALOG LOOP Within each of these paths a number of mea surements can be made to assess the performance of the device operating in that path PC Audio Test enables you to select which measurements and measurement paths you want to test in a given session The paths and measurements are dis played in the Test Explorer window as a hierarchical tree Individual measure ments or entire paths and can be enabled or disabled by clicking in the adjacent check boxes See Chapter 3 for more information about choosing paths and measurements 8 PC Audio Test User s Manual Quick Tour Test Settings Chapter 1 Introduction Dynamic Range DUT Converter Settings Sample Rate Resolution bits PLAY amp RECORD Line econo ono Level References Play D A 0 der P V A A Unity Gain Record A D O dBr R Mic Boost On Stimulus Level 3 dB w Below Reference Level Filters 20kHz AES17 Filters marked must be installed Stimulus Level 60 dB Below Reference Level Filters 20kHz AES17 Filters marked must be instal
69. d ERROR Chan B output signal below 30 dBV Check Mono mode or DUT Pan Balance set to center In Mic In DUTs assign a mono mic signal to both Channels A and B If Channel B is quite low check that the DUT driver software pan or balance controls are centered ADJUSTMENT FAILED 20 adjustment loops done Mic Input slider setting not found On the DUT Properties Configuration Microphone A A check Manual Override Set slider for maximum level and THD lt 1 After 20 tries to find the correct MIC ANALOG LOOP level setting PC Audio Test has given up and you must go to manual override for this path Failure to find the MIC ANALOG LOOP level setting can be due to varying PC Audio Test User s Manual 91 Appendix A Troubleshooting Test Messages 92 signal levels signal interruption non standard DUT driver control or extreme nonlinearity 1n the driver control law ERROR Ap Generator Regulation Error Err Number Err Description The above message indicates a regulation error within the control software when PC Audio Test is adjusting analog level reference This is usually due to unstable or varying signal level or frequency or possibly noise or interference in the DUT A D LevelRef Manual Record A D slider and Generator Amplitude Adjust Last Measurement Chan A 0 00 dBFS THD 0 000 Chan B 0 00dBFS THD 80 000 If Distortion is high and Level low reduce Generator output Adjust Reco
70. d Ripple measurement of the DUT s ADC The Passband Ripple results are displayed as a graph on a linear scale 56 PC Audio Test User s Manual MIC RECORD Measurement Path Chapter 3 Running the Tests MIC RECORD Measurement Path Ee MIC BOOST STORAGE ANALOG TO RECORDING RECORDING MIC IN MEMORY or DIGITAL CONVERTER MUX MIC IN HARD DISK MULTIPLEXER SLIDER Figure 39 MIC RECORD path block diagram Introduction to MIC RECORD A D PC path In MIC RECORD the PC audio device buffers and sets the level of the ana log audio presented at the Mic input converts it to a digital audio signal using the audio device ADC analog to digital converter and stores the audio as a Wave file in PC memory or disk storage The driver software communicating with the sound device provides a Re cord mixer with a volume control for this path usually called the Mic In slider control Other recording sliders may be provided but in most cases the recording multiplexer allows selection of only one at a time In some DUTs the recording multiplexer Mic In volume and the playback mixer Mic In vol ume are addressed by the same slider control You may choose to engage the audio device Mic Boost if you wish The MIC RECORD tests will proceed normally but the results will be noisier by the amount of gain applied by the device s Mic Boost feature Stimulus signals for the MIC RECORD path For both single tone and multitone MIC RECORD
71. designed to provide an optimal interface between a PC audio device and your Audio Precision measurement instrument This chapter provides an overview of the capabilities and requirements of PC Audio Test and gives a quick tour of its features Go to Chapter 2 Getting Ready to install PC Audio Test and begin configuring your system for testing Refer to the Quick Start Guide included with the PC Audio Test materials and as a PDF file on the CD ROM as you familiarize yourself with the appli cation We also recommend reading the AES convention paper Testing Chal lenges in Personal Computer Audio Devices referred to on page 122 and included as a PDF on the CD ROM Overview PC Audio Test is a software application for use with select Audio Precision measurement instruments It provides quick accurate detailed measurements of the audio performance of a PC sound device such as a sound card or a motherboard implementation of a sound device The sound device under test DUT must be part of a personal computer system using Microsoft Windows as the operating system PC Audio Test is comprised of a suite of tests that can completely character ize a PC sound device including level phase distortion noise crosstalk and response measurements for the device s input output recording and playback functions in both the analog and digital domains The PC Audio Test measure ments include all the tests required to satisfy the WHQL PC 2001 standard
72. dio cables illustrated in Figure 29 and also a special cable for testing a mono microphone input while mea suring the Mic In bias voltage as explained on page 49 30 PC Audio Test User s Manual Connecting the Hardware Chapter 2 Getting Ready Figure 31 PC Audio Test Cable Set On the left is the special Mic Bias cable next are the unbalanced input and output audio cables and below is the ground cable Audio Cables The unbalanced audio input and output cables are terminated at the DUT end with a stereo TRS 3 5 mm plug and at the instrument end with BNC con nectors or in some cases RCA connectors fitted with BNC adapters For con venience the cables are color coded at the DUT end to match the standard PC audio device jack colors light blue for Line In and light green for Line Out or Speaker Out Mic Bias Cable The special Mic Bias cable enables you to simultaneously test a mono Mic In function and measure the microphone bias voltage and current capability This cable has a specially wired 3 5 mm TRS plug at the DUT end colored pink to match the standard Mic In color At the instrument end of the cable are two XLR connectors The female XLR is connected to apply signal to the DUT on the tip of the 3 5 mm plug and should be connected to the instrument Analog Output A The male XLR is connected to read the DUT microphone bias voltage on the ring of the 3 5 mm plug and should be connected to the in strument Analog Input A
73. e shortcut button shown at right h Before you can test a PC audio device you must connect the hardware and configure the device as discussed next DUT Selection and Configuration A personal computer or a networked computer system can have many PC sound devices available These can be used independently or in conjunction with each other for multiple channel work Because PC sound devices vary greatly representing many different design goals feature sets hardware imple mentations and software drivers PC Audio Test attaches one or more custom configuration files to each audio device to define DUT and instrument connec tions and driver software settings PC Audio Test User s Manual 15 Chapter 2 Getting Ready DUT Selection and Configuration 16 The DUT Explorer The DUT Explorer enables you to select a PC sound device as the current device under test DUT and configure the DUT and your Audio Precision in strument for testing BUT Explorer a X ESSE Re Creative Sound Blaster PCI o 4 Creative Sound Blaster PCI 1 A Creative Sound Blaster PCI 7 Creative Sound Blaster PCI 3 IE ae Digital Audio P SoundM4 Digital Audio 1 Figure 13 The DUT Explorer showing multiple con figurations for the DUT The configuration numbered 2 Is active The DUT Explorer window shows all PC sound devices available to your PC whether local or across a network connection Choose the sound device to test your D
74. earing system in order to produce measurements usually of noise which correlate well with human observations PC Audio Test User s Manual Appendix D Glossary WHQL Windows Hardware Quality Labs Microsoft s program to ensure hardware compatibility by recommending standards and implementing com patibility testing and verification On the Web at www microsoft com hwdq hwtest default asp WHQL PC2001 The common name referring to the Intel Microsoft docu ment PC 2001 System Design Guide Chapter 11 discusses audio require ments See Appendix E XML Extensible Markup Language XML is a simple very flexible text format derived from SGML ISO 8879 Originally designed to meet the chal lenges of large scale electronic publishing XML is also playing an increas ingly important role in the exchange of a wide variety of data on the Web and elsewhere PC Audio Test User s Manual 119 Appendix D Glossary 120 PC Audio Test User s Manual Appendix E Bibliography This appendix references standards and other documents books and Web links that may be helpful to users of PC Audio Test Audio Standards AES3 1992 Recommended Practice for Digital Audio Engineering Se rial Transmission Format for Two Channel Linearly Represented Digital Au dio Data J Audio Eng Soc vol 40 No 3 pp 147 165 June 1992 The latest version including amendments 1s available from www aes org AES17 1998 AES standard
75. ecifies a particular value or because the PC audio device you are testing does not conform to typical control assignments and cannot be controlled automatically The fields to the right of each slider assignment selector enable you to over ride the PC Audio Test settings and enter a fixed volume setting Your testing for example may require that the PLAY A D volume be always set to a par ticular value rather than be automatically optimized by PC Audio Test See Manual Level Setting on page 81 To set the level manually click the checkbox for that mixer slider The set ting field will become available You can enter the level setting directly in the field or select the level setting using the scroll arrows When a slider control is set to manual all measurements in that measure ment path will be referenced to the signal controlled by your manual setting Measurements in other paths will be unaffected and will continue to operate with automatic level setting Mic Boost Assignment The Mic Boost assignment on the DUT Configuration panel does not turn the Mic Boost function ON or OFF That is done by clicking the Mic Boost checkbox on the Test Settings panel Mic Boost assignment merely selects the driver control for the Mic Boost function If you intend to use Mic Boost in your test be sure that the Mic Boost assignment is set to a valid control usu ally Microphone Boost PC Audio Test User s Manual 21 Chapter 2 Getting Read
76. ecisely 997 001 Hz The frequency of the DUT output is measured and compared to this value Any variation is due to sample rate error in the DUT DAC clock reference The variation is reported as a percentage THD N at PLAY Level Reference After the Level Reference has been set the same 997 Hz tone is analyzed for its distortion as part of the PLAY Level Reference measurement The dis tortion is measured as unweighted THD N total harmonic distortion plus noise across a bandwidth of 10 Hz to 22 kHz This reading usually differs from the results in the PLAY THD N measurement discussed below due to possible differences in stimulus level and filtering Playback Mixer Wave slider position PC Audio Test reads the playback mixer Wave slider position at PLAY Level Reference The position is reported as a step number See the Slider Position sidebar on page 41 Playback Mixer Master Volume slider position PC Audio Test reads the playback mixer Master Volume slider position at PLAY Level Reference The position is reported as a step number See the Slider Position sidebar on page 41 PC Audio Test User s Manual Chapter 3 Running the Tests lt DAFSLvIAr gt lt DAFSLvIBr gt JOdBrA OdBrBi ECO E PLAY Sample Rate Error lt DASRateErr gt PLAY THD N O Level Ref lt DAFSTHDA gt lt DAFSTHDB gt PB Mixer Wave Slider position lt WAVOutSlider gt PB Mixer Master Slider position lt Mast
77. ement Console Connections to instrument 18 Connections hardware 29 Connectors vo ee eV EB we ee eS aid 105 Crosstalk ANALOG LOOP 46 Custom results templates 67 D Urna PRA RSA 43 DOOM semid dawn eee Goes nipi 121 PC Audio Test User s Manual DCOM configuration 2 22 2 F DCOM definition lt veses ad 84 69 GCOMCMG Aw eo ewe Bo ps Ree 72 D D See DIGITAL LOOP measurement path Digital interface characterization 63 DIGITAL LOOP measurement path 63 DIGITAL LOOP path results 104 Digital settings 2 a a ee am SE ow 23 DISIOMION 2 c e o ade a ee E RE E wa 44 DUT configuration 16 DUT device properties 16 DUT Explorer roms bak dd Se 16 DUT selection 04 15 Dynamic range 222260890 wee amp 2m 48 Dynamic range settings 25 E Earthing earth connection See Grounding Error messages o 85 Faders See Sliders Female comnectorS 105 Files PC Audio Test 33 Filters use with PC Audio Test 3 FR See Frequency Response Frequency Response 53 Frequency response settings 26 G Ground cable 12 30 Ground check button 19 Grounding 42 0 64 62066 BS ERA 110 Hardware connections 29 HTM
78. ence Other settings in the Level Reference area of the panel are m A A Unity Gain The A A Unity Gain checkbox sets the Line In slider so that Input Voltage Output Voltage Unity Gain m Mic Boost The Mic Boost checkbox allows you to set the DUT s Mic Boost function ON or OFF for PC Audio Test use Mic Boost adds a fixed amount of gain to the PC audio device Mic In cir cuit for the additional amplification often needed when using a microphone as a source Mic Boost gain is typically 20 dB Not all DUTs or DUT software drivers feature a Mic Boost function THD N Settings THD N Stimulus Level Filters Figure 24 Test Settings THD N settings See the Distortion THD N sidebar on page 44 The THD N distortion measurement applies a 997 Hz signal to the DUT as a stimulus and measures the distortion products created in the DUT By de fault the stimulus level for THD N measurements is the level that corre sponds to 3 dBFS for PLAY measurements or 3 dBr for RECORD and ANALOG LOOP measurements Some standards or measurements may require other THD N stimulus lev els typically O dBFS 1 dBFS or 6 dBFS You can select any of these values or enter a value of your choice in the THD N Stimulus Level setting field When measuring THD N it is not uncommon to use signal filtering such as a low pass filter or a weighting filter in the analysis In PC Audio Test THD N measurements the default is the 20
79. eports To print a report from within PC Audio Test first be sure that the test re sults you wish to report are the current results m PC Audio Test Then simply load the HTML template of your choice into the results viewer and choose File gt Print You can save a formatted report as a PDF file if you have Adobe Acrobat installed on your computer Choose File gt Print gt PDF Writer or an equiva lent command for your system PC Audio Test User s Manual 67 Chapter 4 Viewing and Reporting Results Printing Reports 68 PC Audio Test User s Manual Remote Testing Introduction PC Audio Test can control and test a DUT in another computer over a Win dows network connection by using DCOM a wire protocol for communicat ing with software components on other computers DCOM is a standard feature of Microsoft Windows and is included in with Windows operating sys tem installations In a production environment this capability can smooth operations and save time by enabling you to operate PC Audio Test from a host local computer while performing measurements on a PC audio device in a client or target computer Requirements There are several requirements for remote testing with PC Audio Test which are highlighted here and discussed in detail in following topics The Host Computer m APP 2010 PC Audio Test must be installed on the host local computer m The Audio Precision control software must be installed on the host
80. erSlider gt 39 Chapter 3 Running the Tests PLAY Measurement Path PLAY THD N THD N measurement See the Distortion THD N sidebar on page 44 lt DATHDA gt lt DATHDB gt For the PLAY THD N measurement PC Audio Test inserts the appropriate digital stimulus signal into the PC for DUT playback The THD N stimulus is always a 997 Hz sine wave Depending on your configuration settings the stimulus level may be at 0 dBFS 1 dBFS 3 dBFS 6 dBFS or at a level of your choice AES17 specifies the 1 dBFS stimulus level WHQL PC2001 specifies 3 dBFS The DUT analog output is analyzed for THD N As an option you can ap ply an analyzer weighting or bandpass filter if a THD N measurement is fil tered it is typically with a bandpass filter WHQL however specifies a weighting filter The filter must be installed and available in your Audio Precision instru ment See Test Settings in Chapter 2 for more information on applying filters to the THD N measurements NOTE In accordance with accepted practice for PC sound device measurements PC Audio Test expresses THD N results relative to the PLAY Level Reference rather than to the stimulus tone level PLAY Dynamic Dynamic Range measurement Range See the Dynamic Range sidebar on page 48 lt DADynRngB gt For the PLAY Dynamic Range measurement PC Audio Test inserts a stim ulus signal into the PC for DUT playback The dynamic range stimulus is a 997 Hz sine wave
81. ffice XP versions of Microsoft Excel and Word can open the XML file directly for editing and reformatting If you copy the results file remember to include the style sheet xsl and the HTML template in use to maintain the same formatting and filtering HTML templates The HTML documents that act as templates for the Results Viewer are lo cated in the Reports folder under the PC Audio Test installation folder Four HTML templates are provided with PC Audio Test You can easily add your own custom report template to this collection The templates include m Test Results This is the report used for the default Test Results window display It is comprehensive in that it shows the result of every test and measurement performed by PC Audio Test This template is optimized for on screen viewing Comprehensive This template displays the same comprehensive set of results as Test Results but is optimized for printed output Comprehensive without diagrams This template is the same as Comprehensive but includes only one signal path diagram as compared to seven diagrams in Comprehensive PC 2001 This template produces a WHQL report listing specific items required by PC 2001 optimized for printing PC Audio Test User s Manual Printing Reports Chapter 4 Viewing and Reporting Results You can add custom HTML templates for your own needs Edit one of the templates or design a new HTML document 1n the text editor or Web tool of y
82. generator reference which PC Audio Test refers to as the RECORD Level Reference or 0 dBr rec Do RECORD Level Reference FIRST RECORD Level Reference must be determined before any other recording measurements involving the analog inputs RECORD RECORD PLAY LOOP can be made Line In Recording Slider setting PC Audio Test reads the recording mixer Line In slider position at RECORD Level Reference The position is reported as a step number See the Slider Position sidebar on page 41 THD N measurement See the Distortion THD N sidebar on page 44 For the RECORD THD N measurement PC Audio Test applies a 997 Hz sine wave to the DUT Line Input at a nominal amplitude The THD N stimu lus is always a 997 Hz sine wave Depending on your configuration settings the stimulus level may be at O dBr rec 1 dBr rec 3 dBr rec gt PC Audio Test User s Manual RECORD Measurement Path Chapter 3 Running the Tests Passband Ripple Passband ripple refers to the series of minor peaks and valleys observed in the passband frequency response ofan ADC or DAC This response ripple is a function of converter design and in most modern converters the ripple ampli tude is negligible typically small fractions of a decibel The passband ripple measurement is performed in a similar way to the fre quency response measurement A multitone signal although a different multitone is the stimulus and the DUT output is analyzed for response u
83. he MIC RECORD Frequency Response measurements These results are smoothed and subjected to Compute calculations providing a Passband Ripple measurement of the DUT s ADC The Passband Ripple results are dis played as a graph on a linear scale PC Audio Test User s Manual MIC RECORD Dynamic Range lt MicADDynRangA gt lt MicADDynRangB gt MIC RECORD Frequency Response lt MicADResponse gt MIC RECORD Passband Ripple lt MicADRipple gt 59 Chapter 3 Running the Tests RECORD PLAY LOOP Measurement Path EG LOOP THD N lt ADDATHDA gt lt ADDATHDB gt 60 RECORD PLAY LOOP Measurement Path q E e lt O ENERO ANALOG TO RECORDING RECORDING LINE IN di a K DIGITAL CONVERTER MUX LINE IN OR MIC IN MULTIPLEXER SLIDER Eme gt 0 gt MIXER DIGITAL TO PLAYBACK PLAYBACK LINE OUT ANALOG CONVERTER NAVE MASTER or SLIDER VOLUME SLIDER Figure 40 RECORD PLAY LOOP path block diagram Introduction to RECORD PLAY LOOP A D PC D A path The RECORD PLAY LOOP path is a combination ofthe RECORD and PLAY paths Some of the key measurements for this path were performed in the RECORD and PLAY paths such as the PLAY and RECORD Reference Level measurements Other measurements are established in this path mode Stimulus signals for the RECORD PLAY LOOP path For both single tone and multitone RECORD PLAY LOOP measurements PC Audio Test controls the instrument analog generat
84. he first special run mode 1s called AutoOff In this mode only the mixer line currently being tested is controlled by the PC Audio Test all other mixer controls are unaffected The other controls may be manually set to mute to maximum or to any other setting The quality of the test results results depend on your choices in setting the other controls Some controls will have no effect on the test results others may add noise increase distortion reduce dynamic range and so on Typical Run dialog or shortcut targe command string for AutoOff mode e C Program Files Audio Precision PC Audio pcaudio exe AutoOff Notice that the switch argument is outside of the final quotes This com mand is case sensitive AllMax The second run mode is called AllMax In this mode all mutes are set to OFF channel ON and all volumes are set to maximum PC Audio Test User s Manual Test Failures Appendix A Troubleshooting This mode can be used to circumvent mixer line conflicts or dependencies Some multi channel PC sound devices for example may have additional vol ume controls such as front and rear for surround configurations If you are us ing the front output for your measurement you may have to adjust both the main volume control and the additional front volume control to produce a sig nal at the output In AllMax mode all mixer lines are on and you will be able to measure signal at the output Once you have measured signal a
85. he tip ring sleeve TRS version has three conductors and is ordinarily used as a dual channel stereo unbalanced connection In this configuration the tip is usually connected to the left channel signal high the ring 1s con nected to the right channel signal high and the sleeve is a common signal low at ground potential With three conductors a 14 phone TRS connector can also be used as a sin gle channel or mono balanced connection This configuration 1s found on some professional and semi pro PC sound cards RCA or phono plugs and jacks oe Figure 60 RCA phono connectors RCA plugs and jacks also called phono plugs and jacks have two con ductors and are used for single channel unbalanced connections RCA connec tors are found on some PC audio cards as digital inputs and outputs and sometimes as analog connections RCA connectors are widely used in home stereo and video equipment PC Audio Test User s Manual 107 Appendix C Connector Designations XLR Connectors XLR Connectors Figure 61 XLR connectors In professional and semi pro audio many of the audio connections are made using XLR connectors The XLR designation comes from the Cannon brand XLR series connectors and although XLR has become the common name compatible connectors are made by a number of other manufacturers us ing different designations Some professional and semi pro PC sound devices offer XLR 3 inputs and outputs the
86. ible data types are e Str e Dbl e Lng e Dbl array m Column Four is the value Formatting applied This formatting 1s independent of page formatting you may apply in your report template m Column Five is the Unit for the result value String variables with value formatting applied will include a unit reference in the result value string Such units are shown here in quotation marks Units shown without quotation marks are not included in the result value string m Column Six 1s the Reference for the result when applicable See Chapter 4 for information about HTML report templates PC Audio Test User s Manual 97 Appendix B Results Listings PLAY D A Path Results PLAY D A Path Results Description Collection Name Data Type Formatting Unit LAY Level Reference Ch B FSOV 0 dBrera B DAFSLvIB tr PLAY LevelRef test conditions DALwiRefistCond Str no ATHDA tr PLAY THD N test conditions DATHDTstCona st no Y tr DAldleNoiseB tr PLAY Dynamic Range test conditions DADynRngTstCond St nm PLAY Max Pos Phase Error DAPhaseMax Str o o00 deg PLAY Max Neg Phase Error DAPhaseMin Str o o00 deg PLAY Frequency vs Relative Phase DAResponse Dbl array no deg PLAY Frequency Response test conditions DARespTstCond_ Str no PLAY Frequency Response Limit DAResplimit Str no ARipple bl array In ARipple n DAID IVIVIV UN DID DNDI D DNDIDIDNINDINDINDIC IC AIAI W E O O o bl a
87. ically on Toslink connectors PC Audio Test User s Manual 109 Appendix C Connector Designations Grounding Grounding Figure 65 Heavy gauge grounding cables Proper grounding 1s essential in interconnecting any audio system For PC audio testing we recommend that in addition to the ground connections that are carried in the signal cables you add a low resistance dedicated ground con nection To be effective this connection should be a stranded copper wire of large gauge as short as is reasonable for your interconnection requirements Each end of this ground wire should be soldered to a large low resistance alligator type clip Instrument Analog Connections Audio Precision instruments have both balanced and unbalanced analog an alyzer input and analog generator output connections Generally you should use the instrument balanced connectors with balanced DUT connectors and the instrument unbalanced connectors with unbalanced DUT connectors Instrument Digital Connections Audio Precision instruments have both balanced and unbalanced digital an alyzer input and digital generator output connections The balanced connectors are optimized for the professional AES3 digital format and the unbalanced connectors are optimized for the consumer S PDIF digital format Using a Switcher When testing multi channel PC audio devices or multiple individual devices in the same PC you may find it convenient to programmaticall
88. imulus Level setting field Like the THD N measurements it is not uncommon to use signal filtering such as a low pass filter or a weighting filter in dynamic range measure ments In PC Audio Test dynamic range measurements the default is the 20 kHz AES17 filter The second field in the Dynamic Range settings area al lows you to select a different filter or no filter in your Audio Precision in strument for dynamic range measurements NOTE See the note above regarding hardware option filters for THD N measurements The same applies here PC Audio Test User s Manual 25 Chapter 2 Getting Ready Test Settings Frequency Response settings Frequency Response Stimulus Test File Response Ref way and agm Freq O dB at Line 48kHiResFreqResp M 1 kHz M Mic 24kHiResFreqResp M Figure 26 Test Settings frequency re sponse settings See the Frequency Response sidebar on page 53 Unlike the Level Reference THD N and dynamic range measurements which use single tone stimulus signals the frequency response measurements use multitone techniques with stimulus waveforms stored as digital audio files By default the multitone files selected for frequency response contain the ISO31 set of frequencies at the current sample rate You can select other multitone files from the drop down lists provided Separate selections are available for Line In and Mic In modes due to the possibility of different
89. in fre quency and phase response measurements a multitone wave file that has been prerecorded onto the PC s hard disk during installation is played by the DUT Level Reference measurement Do this FIRST See the Level Reference sidebar on page 38 The PLAY Level Reference measurement is used as the level reference for all other analog measurements made by PC Audio Test PC Audio Test User s Manual 37 Chapter 3 Running the Tests PLAY Measurement Path Level Reference udio testing almost always begins by establishing a reference level usu ally a mid band frequency and often at or near the maximum operating level of a device This level is used as the reference for test results that are expressed in relative terms such as distortion dynamic range or frequency response In re cord playback systems the level produced when a reference recording is played is also used as the reference for the playback of a recorded signal For digital work the mid range frequency is usually chosen to be 997 Hz which is close to the 1000 Hz used in analog testing but is non synchronous with standard sample rates This ensures that the converter under test will be exercised through a maximum number of its possible states Maximum level in a digital system can be defined in a number of ways for PC sound devices maximum digital level is usually considered to be either 0 dBFS or the highest level that produces less than 1 THD N 0 dBFS
90. in the PC and analyzed for lt ADDynRangB gt dynamic range referenced to O dBFS Frequency Response measurement See the Frequency Response sidebar on page 53 For the RECORD Frequency Response measurement PC Audio Test uses a multitone technique An appropriate multitone signal is applied to the DUT RECORD Frequency Line Input at a nominal level Depending on your configuration settings the Response stimulus level may be at O dBr ec 1 dBr rec 3 dBr rec 6 dBr rec lt ADResponse gt or at a level of your choice PC Audio Test User s Manual 55 Chapter 3 Running the Tests RECORD Measurement Path NOTE You can specify a custom multitone signal for frequency response testing Custom multitone signals can be created using the Audio Precision Multitone Creation utility or by downloading files from the Audio Precision Web site at audioprecision com See Frequency Response Settings on page 26 The multitone signal in the DUT ADC output is acquired directly within the PC and is analyzed using FFT techniques resulting in a graph showing both frequency and phase response Passband Ripple measurement See the Passband Ripple sidebar on page 55 RECORD A second multitone and second FFT analysis are automatically performed Passband Ripple during the RECORD Frequency Response measurements These results are smoothed and subjected to Compute calculations to remove response lt ADRipple gt variations providing a Passban
91. in your Audio Precision instrument See Test Settings in Chapter 2 for more information on applying filters to the Dynamic Range measurements Signal to Noise Ratio measurement This Signal to Noise Ratio SNR measurement is unique to the ANALOG LOOP paths both Line In and Mic In It is similar to the MIC ANALOG LOOP Dynamic Range measurement but does not use a low level tone for stimulus or an analyzer notch in measure ment Instead the broadband noise at the Line Out jacks is measured and ex presses as a ratio to the MIC ANALOG LOOP Level Reference Like the THD N and Dynamic Range measurements you can apply a weighting or bandpass filter to the SNR measurement if an SNR measurement is filtered it 1s typically with a weighting filter The filter must be available in your Audio Precision instrument The Dy namic Range filter selection is used as the selection for filtering SNR measure ments See Test Settings in Chapter 2 for more information on applying filters to the Dynamic Range and SNR measurements NOTE Due to the absence of a notch filter in the SNR measurement the results may vary slightly from the Dynamic Range results PC Audio Test User s Manual MIC LOOP Dynamic Range lt AAMicDynRngA gt lt AAMicDynRngB gt MC LOOP SNR lt AAMicSNRA gt lt AAMicSNRB gt 51 Chapter 3 Running the Tests MIC ANALOG LOOP Measurement Path Frequency Response ANLG LOOP Frequency Response measu
92. ing DCOM Chapter 5 Remote Testing E Component Services at B File Action View Window Help e gt Bm Xx Y Console Root E e Component Services Computers a My Computer COM Applications 3 DCOM Config AccStore Class AcroDistx AcroExch Matrix AcroExch AP2700 APWIN AccStore Class AcroDistx AcroExch Matrix AcroExch PDBookmart PDBookmark Application Application AP2700 Application APWIN Application amp L ASF Stream Descriptio ATS ATS 2 ASF Stream ATS ATS 2 Audio Precision PC Au Descripti Authorable Button v amp amp 2 Figure 46 Navigation to PC Audio Test SoundServer COM application Right click on the Audio Precision PC Audio Test SoundServer icon and chose Properties from the menu A tabbed properties dialog box will open u est SoundServer Proper General Location Security Endpoints Identity General properties of this DCOM application Application Name Audio Precision PC Audio Test SoundServer Application ID 9849F738 0F61 4916 94B2 4C8FEFA24D 13 Application Type Local Server Authentication Level Default v Local Path Figure 47 Audio Precision PC Audio Test SoundServer Properties dialog box Gen eral tab On the General tab set Authorization Level to Connect NOTE If the computer s default setting is Connect you may select Default
93. ing in a graph showing both frequency and phase response Passband Ripple measurement Ra Passband ll Ripple See the Passband Ripple sidebar on page 55 lt DARipple gt A second multitone and second FFT analysis are automatically performed during the PLAY Frequency Response measurements These results are smoothed and subjected to Compute calculations providing a Passband Ripple measurement of the DUT s DAC The Passband Ripple results are displayed as a graph on a linear scale Slider Position Volume sliders in a PC audio device control the signal volume in discrete steps A slider may have 32 steps 256 steps or more These sliders can control DSP gain algorithms or dedicated hardware gain circuits in the PC audio de vice The gain mechanisms may follow the slider steps in a linear manner or logarithmically or follow some other gain law This range of characteristics can make automated gain adjustment difficult PC Audio Test can correctly find the correct slider position for device test ing successfully most of the time If unusual DUT characteristics makes this dif ficult you can enter a fixed slider position for the volume sliders associated with a measurement path in the DUT configuration panel Whether automatically located or manually entered the associated slider position for each measurement is recorded and listed in the test results Slider position is always reported as a step number not a decibel value
94. input and output capabilities m the Audio Precision control software The software release version must include support for PC Audio test In this manual we assume that you have an Audio Precision instrument and software compatible with PC Audio Test and that you are familiar with the operation of the instrument Complete information on the operation of these instruments is included with purchase and is also available at the Audio Preci sion Web site Audio Precision Instrument PC Audio Test Support Control Software SYS 2022 SYS 2300 SYS 2500 Instrument configuration does not include either analog or DSP er pia Nona capabilities and DOES NOT support PC Audio Test requirements All PC Audio Test measurements SYS 2222 except DIGITAL LOOP supported APWIN 2 24 or later All PC Audio Test measurements SYS 2322 supported APWIN 2 24 or later rena ena proc SYS 2712 AP2700 3 00 or later SYS 2122 06k ene ee SYS 2722 192k AP2700 3 00 or later ATS 2 not yet supported Check the Audio Precision Web site at audioprecision com for up to date information on the specific Audio Precision instrument models and software versions that support APP 2010 PC Audio Test Recommended Instrument Analyzer Filters Software filters and for SYS family instruments hardware filters can be applied to the analyzer in Audio Precision instruments The filter choices can include high pass low pass and weighting filter options PC Audio Tes
95. ipping the action of a system in flattening and squaring off signal peaks when driven with a signal whose peak amplitude 1s beyond its linear signal handling capability control software for Audio Precision products one of several software programs that control Audio Precision audio test and measurement instru PC Audio Test User s Manual Appendix D Glossary ments APWIN ATS and AP2700 are examples of Audio Precision control software crest factor the ratio of a signal s peak amplitude to its rms amplitude crosstalk unwanted signal coupling from one channel of a multi channel transmission or recording system to another DAC see digital to analog converter dB abbreviation for decibel a ratio unit for expressing signal amplitudes If the amplitudes are expressed in voltage dB 20 log10 V1 V2 If the am plitudes are expressed in power dB 10 log10 P1 P2 Two important points to remember m The dB mimicking our hearing is not a linear unit but a measurement on a logarithmic scale m Decibels are relative units of measure having no meaning in an absolute sense A dB must always be referenced to something to have meaning You can speak of a 4 dB change or a 60 dB signal to noise ratio because these are both relative statements but describe a signal level as 39 dB means nothing All absolute measurements expressed as decibels must have an indication of reference such as dBu dBV dBr and so
96. is dialog from the Windows Run dialog box Type the name of a program Folder document or Internet resource and Windows will open it for you Open dcomenfg mw Cancel Browse Figure 44 Run command line to launch DCOM configuration On the target computer taskbar click Start and then Run and enter dcomcnfg Click OK The Component Services window of the Microsoft Management Console will open BS Component Services LJ EX e File Action view Window Help gt mB e Y Console Root Console Root Component Services EH Event Viewer Local el Services Local 8 Component Services Event viewer Local By Services Local Figure 45 Component Services window First view or change the target computer s default settings by navigating to Component Services gt Computers gt My Computer and right clicking to open the Properties dialog Choose the Default Properties tab select Enable Distributed COM on this computer and verify that Default Authorization Level is set to Connect Close the Properties dialog to return to the Component Services window Access the configuration properties of the PC Audio Test SoundServer COM application by expanding the tree and navigating to Component Services gt Computers gt My Computer gt DCOM Config gt Audio Precision PC Audio Test SoundServer as shown in Figure 46 72 PC Audio Test User s Manual Configur
97. k the connections between your Audio Precision instrument and the DUT m Make your test settings page 9 m Select the measurement paths and measurements you would like to make in your by checking or unchecking the boxes next to the paths or measurements 1n the Test Explorer Now that you are ready click the Run button to begin the test procedure You can watch the progress of your test as status indicators appear next to the measurements in the Test Explorer Measurement results will begin to populate the HTML template in the Results Viewer as the test progresses The yellow box with the arrow indicates a measurement in process The checked green box indicates a measurement successfully completed The red box with the white F marks a measurement that has failed or has been stopped before completion In most cases your test will proceed through the end and stop itself At that point you could print the Test Results shown in the Test Viewer and call it a day Click Stop if you would like to end the test before it completes all the se lected measurements Test Failures When a test fails it is most often due to configuration problems you may have forgotten to specify a driver control or selected a balanced XLR input for your instrument but connected the input cable to the unbalanced BNC In many cases a PC Audio Test dialog box will open with a description of the er ror and a recommended solution If you have a failure that is n
98. led Frequency Response Stimulus Test File Response Ref way and agm Freq O dB at Line 48kHiResFreqResp ed Mic 24kHiResFreqResp Figure 8 Typical Test settings panel Each of the tests has certain properties that can be set such as sample rate stimulus level low pass filtering and so on This collection of properties can be named and saved as a set file See Test Settings on page 22 PC Audio Test User s Manual Chapter 1 Introduction Quick Tour 10 Test Results Report Format Test Results Measurement Channel A Channel B PLAY D A Path PLAY Sample Rate Error PLAY Level Reference FSOW THD N PLAY level Rev PB Wave slider at PLAY Level Ref PB Master slider at PLAY Level Ref PLAY Level Ref test conditions O dBFS O dBr PLAY THD N 28 961 dBr 33 623 dBr PLAY THD N test conditions THD test level O dBFS Filter None PLAY Dynamic Range 49 811 dBr 48 992 dBr PLAY Idle Noise PLAY Dynamic Range Test Cond Dynamic Range test level 60 dBFS Filter None PLAY Max Positive Phase Error 0 30 deg PLAY Max Negative Phase Error 166 50 deg Play D A Frequency Response a vama OMAN Figure 9 The Results Viewer The Results Viewer provides an HTML formatted view of the current XML test results updated 1n real time Current results can be named and saved as an xml file PC Audio Test User
99. m buzz and even radio frequency interference into the audio signal greatly reducing the accuracy of any measurements Ground Check Test Complete o Ratios of the AC Mains frequency and harmonics 45 Hz to 1 2 kHz J to the average noise floor 1 2 kHz to 3 5 kHz Hum Ratio 24 dB 20 dB Noise Floor 135 dBY 135 dBY High Hum Ratio numbers gt 6 dB with strong AC mains frequency peaks may indicate a ground connection problem Use of a Ground strap from the AP System chassis to the DUT chassis may reduce this Figure 17 Ground Check report The Ground Check button tests your connections for ground related prob lems such as these The test measures the ratio of mains frequency and mains harmonics peaks in the 45 Hz to 1 2 kHz range to the average noise floor in the 1 2 kHz to 3 5 kHz range Ratios greater than 10 dB may indicate ground connection problems Low Frequency Spectrum with No Signal J D E9 2 Low Frequency Spectrum with No Signal uy Hz Hz Figure 18 Ground Check graphs Left shows 24 dB and 20 dB ground ratios right shows negligible ground interference If your system exceeds a 10 dB ratio in either channel any subsequent mea surements you make in this configuration are suspect Check the integrity of PC Audio Test User s Manual 19 Chapter 2 Getting Ready DUT Selection and Configuration your cables their routing proximity to devices that may couple
100. magnetically or electrostatically etc and be sure you have a low impedance large gauge ground connection such as the ground cable supplied with PC Audio Test be tween your Audio Precision instrument and the DUT see page 30 Assigning Mixer Sliders E Volume Control a E Options Help Volume Control Wave Mic Volume Line In Balance Balance Balance ER a Rs AA Volume Volume Volume E E E o Mic Volume Line In l l l Balance Balance dlje Ae a ES Y F gr GF q d i i i 1 C Mute all Mute Volume Volume Creative Sound Blaster PCI g i J C Select Select Figure 19 Typical Playback left and Recording Mixer windows Each PC audio device has hardware components and software driver ele ments that work together to route and control the audio signal through the de vice These controls are usually displayed in one of two windows or window panels often called mixers The Playback mixer window shows controls that select and adjust signals routed to the Line Out jacks and the Recording mixer window shows controls that select and adjust the signal to be routed to the re cording ADC The mixers offer slider volume and balance controls Mute and Select switches and often include tone controls controls for effects such as surround reverberation or wide stereo settings NOTE For testing purposes all other PLAY mixer sliders CS
101. mation The User Information dialog box enables you to enter a Company Name Division name and User Name that persists across tests This information is entered as the default information in the Test ID for a New Test To check or enter User Information choose Tools gt User Information from the Main menu See Test ID on page 27 28 PC Audio Test User s Manual Connecting the Hardware Chapter 2 Getting Ready Connecting the Hardware A complete set of tests requires analog audio connections between the Au dio Precision instrument generator and the DUT inputs and from the DUT outputs to the instrument analyzer Some DUTs may also require digital audio input and output connections between the DUT and the instrument Mic Bias Cable Analog Audio Go ANALOG o OG OUTPUTA OUTPUT B o OG INPUT A Ine Bo as dos 698 Zoo Yoo 6 jo Besse a DIGITAL INPUT IIIN AA a O O O o RE CHANNELA CHANNELB 22 ODO OOO 00 te Audio Precision Instrument O Ground Connection Figure 29 Typical audio and ground connections between a DUT and an Audio Precision instrument for PC Audio Test When making these connections care must be taken that level impedance balanced unbalanced configuration and XLR pin connections are correctly set An additional electrical common connection usually called a gr
102. means zero decibels full scale 0 dBFS is defined as the level at which the positive and negative peaks of a sine wave just touch the maximum numerical values available in the coding system For 16 bit PCM these peak values in decimal two s complement are 32767 and 32768 0 dBFS is the maxi mum level at which a sine wave can be recorded without digital overload NOTE Many PC audio devices limit the audio input to the ADC to pre vent audio overload With such devices it is impossible to attain 0 dBFS in recording and a somewhat lower maximum level must be specified This reduced level reference can vary from model to model 1 THD N means one percent total harmonic distortion plus noise often simply called 1 distortion Most digital devices have distortion well be low one percent except near digital overload and this alternate statement of maximum level can provide a reference near 0 dBFS NOTE Some PC audio devices have very low distortion right up to digital overload and never exhibit 1 distortion Some poorly de signed devices exhibit distortion higher than 1 throughout much of their range In either case determining a reference level by finding the 1 distortion point can be very difficult Other levels below 0 dBFS such as 1 dBFS 3 dBFS 6 dBFS and so on can be specified for certain standards and tests For PLAY Level Reference PC Audio Test inserts the appropriate digital stimulus signal into
103. measurements PC Au dio Test controls the instrument analog generator providing the appropriate analog stimulus signal for each measurement Level Reference measurement See the Level Reference sidebar on page 38 The MIC RECORD Level Reference measurement is used as the level ref erence for recording measurements made by PC Audio Test NOTE You must perform this measurement before other MIC RECORD or RECORD PLAY LOOP path measurements PC Audio Test User s Manual 57 Chapter 3 Running the Tests MIC RECORD Measurement Path MIC RECORD Level Reference lt MicADFSLVIA gt lt MicADFSLvIB gt 0 dBr A rec 0 dBr Brec Rec mixer Mic In Slider position lt MicLinelnSlider gt mic REC THON lt MicADTHDA gt lt MicADTHDB gt 58 To establish the MIC RECORD Level Reference PC Audio Test applies a 997 Hz sme wave to the DUT Mic Input sets the DUT record multiplexer Mic In slider to the MIC ANALOG LOOP reference setting 1f available other wise it is set to the center of its range and varies the level of the applied sig nal to locate the level one step below the level that produces 1 THD N in the DUT output This point is considered to be O dBFS See RECORD Level Reference Settings on page 24 This amplitude is set as the instrument generator reference which PC Audio Test refers to as the MIC RECORD Level Reference or O dBr pec Do MIC RECORD Level Reference FIRST MIC RECORD Level Reference m
104. method for digital audio engineering Mea surement of digital audio equipment J Audio Eng Soc vol 46 No 5 pp 428 447 May 1998 The latest version is available from www aes org IEC60958 3 2000 Digital audio interface Part 3 Consumer applica tions International Electrotechnical Commission Geneva www iec ch Audio Test and Measurement Dunn Julian Measurement Techniques for Digital Audio Audio Preci sion Press Beaverton Oregon January 2003 www audioprecision com Metzler Bob Audio Measurement Handbook Audio Precision Press Beaverton Oregon August 1993 www audioprecision com DCOM D0COM DCOM Unleashed Unleashed Series by Randy Abernethy Randy Abernethy Randy Morin Jesus Chahin Randy Charles Morin Pub lisher MacMillan Publishing Company Book and CD ROM edition April 1999 ASIN 0672313529 PC Audio Test User s Manual 121 Appendix E Bibliography Audio in Personal Computers Inside Distributed Com Mps by Guy Eddon Henry Eddon Publisher Microsoft Press Book and CD ROM edition April 1998 ISBN 157231849X Learning Dcom by Thuan L Thai Thuuan L Thai Andy Oram Editor Publisher O Reilly amp Associates Ist edition April 1999 ASIN 1565925815 Professional Dcom Programming by Dr Richard Grimes Publisher Wrox Press Inc Ist edition June 1997 ISBN 186100060X Audio in Personal Computers Harris Steven PhD and San
105. must be muted balance and EQ or tone controls if any must be set to their neutral positions and all effects such as Surround Reverb or Wide Stereo must be disabled PC Audio Test must be able to control routing and level for each audio de vice under test The program queries the driver software for the DUT and pro vides lists of all the volume controls available for the relevant DUT inputs and outputs You must select the mixer assignment control from the list for each of the DUT inputs and outputs In many cases there is only one reasonable selection such as Microphone for the Mic input but because the different architecture 20 PC Audio Test User s Manual DUT Selection and Configuration Chapter 2 Getting Ready DUT Driver Software Mixer Assignment Manual Override Master volume Control d aroa oe ME at mem E pecad o evom e O E A Microphone 4 4 150 E Figure 20 DUT Mixer slider assignments and naming conventions used by manufacturers it may not be possible to auto matically choose the appropriate volume control for your intention Automatic and manual level setting In the course of making its various measurements PC Audio Test will auto matically adjust the volume level of various mixer sliders In most cases the automatic level setting will give you the best results However you may want to manually set a particular driver control either be cause your test sp
106. n the previous page Due to converter muting the Dynamic Range measurement is usually cho sen for noise measurements in digital devices However since there are no con verters in the ANALOG LOOP paths the SNR measurement can also be used SNR measurements are made with no stimulus signal and the device input shorted or terminated in a typical source impedance The device output signal often filtered with a weighting filter is applied to a broadband audio meter and this value is compared to the reference level and expressed as a ratio Re sults of this measurement will usually differ from Dynamic Range results due to the effect of the notch filter used in that technique Most PC audio devices have relatively high impedance inputs and the level of the device output noise can vary greatly with changes in input source impedance With an Audio Precision generator connected to the input but with no signal applied the source impedance presented to the DUT is 40 Q bal anced and 20 Q unbalanced Higher source impedances may degrade SNR re sults When SNR is measured using the Mic input care must be taken to minimize cable noise and pickup of spurious signals in the input connections PC Audio Test User s Manual MIC LOOP Line In Level lt AAMiclInLvlrA gt PB mixer Mic In Slider position lt MiclnSlider gt Mic In Boost Gain lt AABoostGain gt Mic in Gain Max Mic In Bias Voltage lt MiclnSupplyV gt
107. nd determined the mixer controls that af fect your measurement path you can optimize you test by manually muting unused controls and optimizing those 1n the path Typical Run dialog or shortcut targe command string for AllMax mode e C Program Files Audio Precision PC Audio pcaudio exe AllMax Notice that the switch argument is outside of the final quotes This com mand is case sensitive Manual Override Some PC audio devices do not use the Windows Mixer API at all but use instead use their own proprietary drivers In such cases it is necessary to use the PC Audio Test manual override function for each test group being tested Each test path has an associated manual override checkbox on the DUT Configuration Properties panel Check the box and then adjust the associated mixer control setting For each test path you can manually set the proper test signal reference level while monitoring control software displays Once this level has been es tablished the tests for that group can be run and results will be generated based on this reference value Manual override allows you to test PCaudio devices that do not support the Windows Mixer API You must carefully optimize your settings to ensure the best performance of the DUT See detailed instructions for operating PC Au dio Test in manual override beginning on page Test Failures Connection and Configuration Many test failures are cause by improper connection or c
108. nd then reports the difference due to slider resolution as the Unity Gain Error Next PC Audio Test adjusts the instrument analog generator to find the point just below that which produces 1 THD N at the Line Out jack The voltage at the Line Out jack is measured and reported as the ANALOG LOOP Level Reference The generator voltage is measured and reported as the DUT Input Level Level Reference with Unity Gain deselected There may be circumstances where DUT characteristics or measurement specifications do not allow a forced unity gain condition In that case deselect Unity Gain on the Test Settings panel With Unity Gain deselected PC Audio Test searches for the signal that can be applied to the Line In jacks while producing less than 1 THD N at the PC Audio Test User s Manual ANLG LOOP Level Reference lt AAFSLvIA gt lt AAFSLvIB gt 0 dBr Apay 0 dBr BpLay ANLG LOOP Unity Gain Error lt AAUnityGainErrA gt lt AAUnityGainErrB gt 43 Chapter 3 Running the Tests ANALOG LOOP Measurement Path Output jacks for any mixer Line In volume slider setting The voltage at the Line Out jack 1s measured and reported as the ANALOG LOOP Level Refer ence The generator voltage is measured and reported as the DUT Input Level THD N at ANALOG LOOP Level Reference After the Level Reference has been set the same 997 Hz tone is analyzed lt AAFSTHDA gt for its distortion as part of the ANALOG LOOP Level Reference
109. not available click Add and enter the name In the Permissions box click Allow 74 PC Audio Test User s Manual Connecting the Hardware Chapter 5 Remote Testing Audio Precision PC Audio Test SoundServer Properties E3 General Location Security Endpoints Identity Which user account do you want to use to run this application The interactive user The launching user This user User Password Confirm password Figure 50 Audio Precision PC Audio Test SoundServer Properties dialog box Identity On the Identity tab select This user and enter the technician s user name and password in the fields Connecting the Hardware See Chapter 2 for detailed information about hardware connections For re mote testing of a PC audio device in a target computer you must connect the audio and ground connections from your Audio Precision instrument to the target PC audio device The instrument APIB control connection remains con nected to the host computer See Figure 51 Network Connection APIB Connection Remote Computer with DUT fam ad Mic Bias Cable ne Ly Alia Y Ep LE E EE Sena A A D o a Q HO a 2 es m NO Ground Audio Precision Instrument Connection Figure 51 Remote test configuration Local Computer PC Audio Test User s Manual 75 Chapter 5 Rem
110. ntrol For maximum level and THD lt 1 Take a new measurement Figure 56 The ANALOG LOOP manual ad justment dialog This dialog tells you the measured level and distortion at the DUT output By adjusting the Line In control volume either from the DUT Configuration panel or from the DUT s playback mixer find the maximum level possible that produces less than 1 distortion Monitor the control software readings and click the Yes button in the dialog box to make a new measurement As you raise the level there will usually be a threshold at which the distortion in creases greatly set the level just below this point If the lowest setting of Line In still produces more than 1 distortion and level is high set the Line In control at lowest active setting Adjust the instru ment Analog Generator level downward a Bar Graph control is available in the control software display to set and view the generator level until you find the find the maximum level possible that produces less than 1 distortion PC Audio Test User s Manual Test Failures Appendix A Troubleshooting NOTE You may notice high distortion readings at very low control settings while making these settings The ranging of the instrument input circuits will amplify system noise under conditions of very low signal and the noise reading will be expressed as a distortion reading Then continue with your test Manual RECORD level control setting See RECORD
111. o Noise Ratio test conditions _ AAMicSNRTstCond fst ne J MIC LOOP Max Pos Phase Error AAMicPhaseMax Str ooo0 deg MIC LOOP Max Neg Phase Error AAMicPhaseMin St ooo0 Jog MIC LOOP Frequency vs Relative Phase AAMicResponse Dblarray_ Jno deg MIC LOOP Frequency Response test conditions AAMicRespTstCond st ne J MIC LOOP Frequency Response Limit AAMioRespLimit fst Jo 100 PC Audio Test User s Manual RECORD A D Path Results Appendix B Results Listings RECORD A D Path Results cren rm us REC Line In Level REC Level Ref Ch A FSIV 0 dBrreo REC THD N test conditions ADTHDTstCond st no REC Dynamic Range test conditions ADDynRngTstCond Str no REC Max Pos Phase Error ADPhaseMax Str f o o00 deg REC Max Neg Phase Error ADPhaseMin Str 0 000 deg REC Frequency Response Limit JADResplimit st fno J REC Passband Ripple Limit ADRippleLimit st no REC MIC Frequency Response Limit JaDMicResplimit st fn These results are not used when the RECORD path measurements are performed using the mic input for PCs that have no Line Input typical of many notebook computers Instead the results marked with are used PC Audio Test User s Manual 101 Appendix B Results Listings MIC RECORD A D Path Results MIC RECORD A D Path Results Description Collection Name MIC REC Level Reference Ch A MIC REC Level Reference Ch B MIC REC THD N MIC REC Level Ref Ch A MIC REC THD
112. oftware and hardware installa tion instructions Refer to the Quick Start Guide included with the PC Audio Test materials and as a PDF file on the CD ROM as you familiarize yourself with PC Audio Test File Edit view Tools Window Help as ala sal n a Test Explorer E ps Untitled Test1 D Test Settings G Test ID Be gt PLAY D A Path BIO Level Reference BIL THD N BIL Dynamic Range BIL Frequency Response BIL Passband Ripple BIC ANALOG Loop A A Path BIC Level Reference BIL THD N BIL Dynamic Range BIC Frequency Response BIL crosstalk Filters BAS mic ANALOG LOOP A A Path BIL Level Reference BIL THD N BIL Dynamic Range BADD Frequency Response BIO rec A D Path BIC Level Reference BIL THD N BIL Dynamic Range BIL Frequency Response BIL PassBand Ripple DUT Explorer Fx E My Computer 8 Creative Sound Blaster PCI P Creative Sound Blaster PCI 1 Y Soundmax Digital Audio J SoundMAX Digital Audio 1 EN PC Audio Test Results Detailed Test Results PLAY ANALOG MIC RECORD REC PLAY DIGITA Device and Test Information Device Under Test Model Serial Number Operator name Operator company Operator division Date Time test started Comments Creative Sound Blaster Channel A PLAY D A Path Measurement PLAY Sample Rate Error PLAY Level Reference FSOV THD N PLAY level Rey PB Wave slider at PLAY Level Ref
113. on See dBu dBV dBr dBFS decibels referenced to digital full scale FS where O dBFS 1s the rms value of a sine wave whose positive peak just reaches positive full scale For everyday use 0 dBFS can be considered to be the maximum digital ampli tude available within a system However it should be noted that because 0 dBFS has been defined for a sine wave waveforms with lower crest factors can exceed 0 dBFS by as much as 3 01 dB before incurring digital clipping See crest factor and digital clipping dBm decibels relative to a reference value of 1 milliwatt dBm is a power unit and requires knowledge of power levels voltage and current or voltage and impedance or current and impedance rather than merely voltage This term has historically been associated with a measurement of audio levels in professional use but it is rarely correctly applied and should not be used ex cept in certain very specific circumstances As a unit of power the voltage value of a dBm will vary with the circuit impedance Use the term dBu instead See dBu dBr decibels relative to an arbitrary reference value r The reference value must be stated for this to be a meaningful unit The dBr can be a handy shortcut during tests allowing you for example to measure a specific voltage and note it as your reference 0 dBr and then to express further measurements in dBr relative to this level PC Audio Test User s Manual 115 Appendix D Glossary dBu
114. onfiguration Be sure your cables are connected properly Check that the DUT configuration panel is set to enable the proper instrument inputs and outputs and that the DUT driver software has the appropriate control selected for each measure ment path See the DUT Configuration panel page 16 PC Audio Test User s Manual 79 Appendix A Troubleshooting Test Failures 80 Ground Check Improper grounding can cause poor results and even test failures by intro ducing high levels of interfering noise into the system Be sure to connect a heavy ground connection between the instrument and the computer fitted with the DUT Click Ground Check on the DUT configuration panel to evaluate your ground connection See Ground Check page 19 Level Reference Failures If connection and configuration are properly set up and grounding is opti mized most Level Reference failures will be due to atypical design of the as sociated DUT function Most DUTs fall within a standard design range but some will add non standard switches or volume controls design controls with very coarse or non linear volume steps or add unpredictable compression or peak limiting The automatic level characterization algorithms of PC Audio Test are quite sophisticated but cannot anticipate non standard DUT architectures In such cases you must manually set levels in the affected signal path dis abling the PC Audio Test automatic level setting algorithms and instead u
115. ons of a signal or between the highest am plitude signal that a device can linearly handle and the noise level of the de vice FFT fast Fourier transform a technique to compute the amplitude versus frequency and phase versus frequency information from a set of amplitude versus time samples of a signal FR PCQAM 1 abbreviation for Frequency Response measurement FSIV PC2001 abbreviation for Full Scale Input Voltage FSOV PC2001 abbreviation for Full Scale Output Voltage ground loop an inadvertent signal path formed when interconnecting the chassis of two or more pieces of equipment each possessing a safety ground Ground loops can cause hum related interference instrument in Audio Precision terms the hardware component of an Au dio Precision test and measurement system controlled by its control software PC Audio Test User s Manual Appendix D Glossary System One System Two System Two Cascade ATS 2 and the 2700 series are examples of Audio Precision instruments System Two and System Two Cascade are compatible with APP 2010 PC Audio Test ISO International Organization for Standards the largest of the many in ternational groups for technical and industrial cooperation The ISO is based in Geneva Switzerland limits testing testing in which measurements are compared to acceptable values so that a pass fail decision may be made line level a relatively high amplitude range suitable for transmission of
116. or providing the appro priate analog stimulus signal to the DUT inputs for each measurement THD N measurement See the Distortion THD N sidebar on page 44 For the RECORD PLAY LOOP THD N measurement PC Audio Test ap plies a 997 Hz sine wave to the DUT Line Input at a nominal amplitude The THD N stimulus is always a 997 Hz sine wave Depending on your configu ration settings the stimulus level may be at O dBr rec 1 dBr rec 3 dBr rec 76 dBr rec or at a level of your choice AES17 specifies the 1 dB stimulus level WHQL PC2001 specifies 3 dB PC Audio Test User s Manual RECORD PLAY LOOP Measurement Path Chapter 3 Running the Tests This signal is routed through the DUT ADC and digitally recorded as a tem porary wave file The file is then played and routed through the DUT DAC and to the Line Out jacks The DUT analog output is analyzed for THD N As an option you can apply an analyzer weighting or bandpass filter if a THD N measurement is filtered it is typically with a bandpass filter WHQL however specifies a weighting filter The filter must be installed and available in your Audio Precision instru ment See Test Settings in Chapter 2 for more information on applying filters to the THD N measurements NOTE In accordance with accepted practice for PC sound device measurements PC Audio Test expresses lt SKIP gt results relative to the Level Reference rather than to the stimulus tone level Dyn
117. osing File gt Save As or open a previously saved test file by choosing File gt Open Only one test can be open at a time The document Personal Computer Audio Quality Measurements PCAQM which has been an important resource for Microsoft s WHOL audio standards and also for our work identifies measurement paths using abbrevia tions like PC D A Personal Computer to Digital to Analog These PCAQM abbreviations are used in the Test Explorer and in documentation where appro priate 34 PC Audio Test User s Manual The Measurement Paths Chapter 3 Running the Tests The first two selections under the test level are Test Settings and Test ID Double clicking either of these opens dialog boxes that enable you to set vari ous technical and administrative preferences These are discussed in detail in Chapter 2 Below Test ID are the various test measurements each under a measure ment signal path branch such as PLAY or RECORD The Measurement Paths After the Test Settings and Test ID branches are the seven measurement paths A measurement path represents the configuration of hardware and soft ware to test a particular set of functions in the DUT Not all PC audio devices will have all of these paths available The measurement paths are m PLAY Digital to Analog Playback PC D A This measurement path tests the digital to analog converter DAC and the analog output circuit The overall level reference for all measuremen
118. ot easily solved check for more information in Appendix A Troubleshooting PC Audio Test User s Manual PLAY Measurement Path Chapter 3 Running the Tests PLAY Measurement Path 3 gt t STORAGE DIGITAL TO PLAYBACK PLAYBACK LINE OUT MEMORY or ANALOG CONVERTER WAVE MASTER or HARD DISK SLIDER VOLUME SLIDER Figure 34 PLAY path block diagram Introduction to PLAY PC D A path In PLAY the PC sound device normally reads a digital audio file from the PC disk storage or memory converts the audio to an analog signal using a DAC digital to analog converter amplifies conditions and routes the signal to the Line Out analog output jacks The driver software controlling the PC sound device provides a Playback mixer with a volume control for this path usually called the Wave slider Additionally there is often a second Master or Volume control slider Other PLAY sliders and features may be provided NOTE For testing purposes all other PLAY mixer sliders must be muted balance and EQ or tone controls if any must 5 be set to their neutral positions and all effects such as Surround Reverb or Wide Stereo must be disabled Stimulus signals for the PLAY path For single tone PLAY measurements PC Audio Test inserts the appropriate digital stimulus signal into the PC The DUT plays this signal as 1f it were a wave file from the PC s hard disk For multitone measurements used
119. ote Testing Remote Testing with DCOM Remote Testing with DCOM Once you have installed PC Audio Test on the target computer configured DCOM and made the audio and grounding connections remote testing 1s just as easy as local testing cal In the DUT Explorer toolbar click the Network button labeled Connect to a Remote Computer Browse to the target machine and click OK Select Computer E Select a remote computer you would like to test The remote computer must be running the PC Audio Test server tools Er Figure 52 Remote computer browser dialog This will reveal the DUTs installed in the target computer and they will ap pear in the DUT explorer in the target computer s branch Select the DUT for testing and proceed with your test as described in Chapter 3 CUT Explorer a X eX e oe pa My Computer EME Soundmas Digital Audio e SoundM as Digital Audio 1 E EMiEng jaket a Creative Sound Blaster PCI Creative Sound Blaster PCI 1 4 Creative Sound Blaster PCI 2 Figure 53 Choosing a DUT on a remote computer 76 PC Audio Test User s Manual Appendix A Troubleshooting Compatibility with Windows APIs Most applications communicating with the Microsoft Windows operating system to control multimedia audio streams do so using the APIs provided with the operating system An API is an application programmer 8 interface and the two APIs used in PC
120. oth Channel A and Channel B within the DUT In other words the DUT monos the input This 1s often the case with the motherboard PC audio device implementations in laptop and notebook computers PC Audio Test User s Manual Test Messages Appendix A Troubleshooting ADJUSTMENT FAILED 20 adjustment loops done Record slider setting not found On the DUT Properties Configuration Record A D check Manual Override Set slider for maximum digital level and THD lt 1 After 20 tries to find the correct MIC RECORD level setting PC Audio Test has given up and you must go to manual override for this path Failure to find the MIC RECORD level setting can be due to varying signal levels signal interruption non standard DUT driver control or extreme nonlinearity in the driver control law PC Audio Test User s Manual 95 Appendix A Troubleshooting Test Messages 96 PC Audio Test User s Manual Appendix B Results Listings Introduction This Appendix contains comprehensive lists of all test results XML data tags by measurement path Collection names and other information that may be helpful in designing tests and HTML re port templates are included m Column One 1s the Description of the measurement m Column Two is the Collection Name The collection name is the string variable you must use in report templates to return a particular result value m Column Three 1s the Data Type for that collection name Poss
121. ound or earth connection will often improve the quality of the measurements by mini mizing ground related noise problems Connect the ground cable between an instrument ground lug and a grounded screw or other grounded point on the target computer chassis near the DUT jacks Typical PC audio device Inputs and Outputs Most PC audio devices have at least a monaural Mic Input and a stereo Line Speaker Output Most also have a stereo Line Input some separate the Line and Speaker Outputs and some add a Digital Input and Output These connections are almost always in the form of 3 5 mm jacks and are often labeled with graphical symbols and colored jack designations as shown in Figure 30 PC Audio Test Users Manual 29 Chapter 2 Getting Ready Connecting the Hardware Figure 30 Typical PC sound device connections Not all sound devices will have all these connec tions and not all will use these colors or these sym bols Typically the pink or red jack 1 is the Mic input usually monaural The blue jack 2 is the Line input the green jack 3 is the primary Line Speaker output and the black jack 4 is the secondary Line Speaker output The yel low jack 5 is often the Digital output although some manufacturers desig nate it a multi purpose Versatile jack with selectable features PC Audio Cable Set The cable set Figure 31 provided with PC Audio Test includes the ground cable and the unbalanced input and output au
122. our choice and save it in the Results folder Result values are entered into re port templates as XML data tags For a complete listing of PC Audio result data tags see the tables in Appendix B The four HTML templates provided all use the cascading style sheet named pc audio test results css for formatting If you copy these templates or a new one you have created by editing a template be sure to copy the style sheet to the new location too To add your custom HTML document to the Results Viewer template list you must edit the file reports xml Open the file in a text editor and insert a new line listing the filename and list name of your new file as shown in Fig ure 43 2 3 4 5 f 6 7 8 9 0 1 t l lt xml version 1 0 gt 2 reports xmlns http www audioprecision com pcaudio reports gt 3 lt report href test_results html title Test Results gt 4 lt report href comprehensive index comprehensive report htn title Comprehensive Report gt lt report href comprehensive_nodiagrams index_comprehensive_report htm title Comprehensive Report no diagrams gt lt report href PC2001 pc2001 test report htu title PC2001 Test Report gt b lt report href My _New_Report htn title My New Report gt 8 lt reports gt Figure 43 Edited reports xml showing addition of My New Report at line 7 Printing R
123. r NO to accept the current setting ERROR Line In or Line Out Channel Connections are Reversed Check DUT Connections and Configuration Channel A and Channel B connections for either the DUT inputs or out puts have been switched one for the other ADJUSTMENT FAILED 20 adjustment loops done Unity Gain slider setting not found On the DUT Properties Configuration Input A A check Manual Override Set slider for maximum level and THD lt 1 After 20 tries to find the correct ANALOG LOOP level setting PC Audio Test has given up and you must go to manual override for this path Failure to find the ANALOG LOOP level setting can be due to varying signal levels signal interruption non standard DUT driver control or extreme nonlinearity in the driver control law 90 PC Audio Test User s Manual Test Messages Appendix A Troubleshooting Mic A A LviRef DUT Configuration Mic In control selected is Not a Microphone control type Use anyway Some DUTs use the same physical connections and mixer controls for Line In and for Mic In When this setting 1s selected PC Audio Test checks to be sure it is not a mistake ERROR Chan A output signal below 30 dBV Check Connections and DUT Properties Configuration This message usually means there is no signal which usually points to a connection problem a DUT or instrument configuration problem or an extra DUT software driver mixer control that is not enable
124. rconnection and is often the cable shield connection as well m Balanced Balanced refers to inputs outputs and interconnections that use three conductors where one conductor carries the signal high a second conductor carries the signal low and a third conductor is at the system ground The ground conductor can be grounded at one or both ends of the interconnection and is also the cable shield connection In a balanced connection neither side of the audio signal is at ground potential Male and female plug and jack Most connectors can be divided into male and female designations the male having one or more probes and the female corresponding receptacles A plug is usually considered to be a male connector and a jack is a female connector Circuit outputs are often but not always provided on male connectors and circuit inputs are often available as female connectors PC Audio Test User s Manual 105 Appendix C Connector Designations 3 5 mm plugs and jacks 3 5 mm plugs and jacks Ring Signal High ip Right Sleeve Sleeve Tip Signal High Signal gti Signal High Cem ai Low Ground TS Tip Sleeve TRS Tip Ring Sleeve Mono Plug Stereo Plug Figure 58 3 5 mm TS and TRS connectors 3 5 mm connectors are sometimes called mini or mini phone plugs or jacks Due to their compact size these are commonly used as input and output connectors on PC sound cards and on notebook computer sound
125. rd A D Manual Override slider control for maximum digital level and THD lt 1 Caution When Levels are at O dBFS Distortion readings are inaccurate Take a new measurement The above message appears during the RECORD manual override level setting procedure This dialog reports the current level and distortion and with the control software and PC Audio Test digital meter displays is an aid to DUT control adjustment Click YES to submit a new setting or NO to accept the current setting ERROR Record Input Channel Connections are Reversed Check DUT Connections and Configuration PC Audio Test User s Manual Test Messages Appendix A Troubleshooting Channel A and Channel B connections for either the DUT inputs or out puts have been switched one for the other ERROR Both channels have signal with only Chan A Input DUT feeds both channels with Monaural input Either by design or in the DUT driver mixer configuration Channel A is connected to both Channel A and Channel B within the DUT In other words the DUT monos the input This is often the case with the motherboard PC audio device implementations in laptop and notebook computers ADJUSTMENT FAILED 20 adjustment loops done Record slider setting not found On the DUT Properties Configuration Record A D check Manual Override Set slider for maximum digital level and THD lt 1 After 20 tries to find the correct RECORD level setting PC
126. rement See the Frequency Response sidebar on page 53 For the MIC ANALOG LOOP Frequency Response measurement PC Au dio Test uses a multitone technique PC Audio Test causes your Audio Preci sion instrument analog generator to output an appropriate multitone file for your test NOTE You can specify a custom multitone file for frequency response testing Custom multitone files can be created using the Audio Precision Multitone Creation utility or by downloading files from the Audio Precision Web site at audioprecision com See Frequency Response Settings on page 26 The multitone in the DUT analog output signal is analyzed in your instru MIC LOOP ment using FFT techniques resulting 1n a graph showing both frequency and Frequency vs phase response Phase 52 PC Audio Test User s Manual RECORD Measurement Path Chapter 3 Running the Tests RECORD Measurement Path Es 4 4 STORAGE ANALOG TO RECORDING RECORDING LINE IN MEMORY or DIGITAL CONVERTER MUX LINE IN HARD DISK MULTIPLEXER SLIDER Figure 38 RECORD path block diagram Introduction to RECORD A D PC path In RECORD the PC audio device buffers and sets the level of the analog audio presented at the Line input converts it to a digital audio signal using the audio device ADC analog to digital converter and stores the audio as a Wave file in PC memory or disk storage The driver software communicating with the sound device provides a Re cord mi
127. rray o LAY Passband Ripple Ch B Ripple no LAY Passband Ripple test conditions ARippleTstCond MN PLAY Passband Ripple Limit DARippleLimit array z O IDJO I gt o no no z 98 PC Audio Test User s Manual ANALOG LOOP A A Path Results Appendix B Results Listings ANALOG LOOP A A Path Results Description Collection Name Data Type Formatting Unit _ A AUTO Jor fimo fas PB mixer Line In monitor slider position ANLG LOOP Level Ref LineMonOutslider m ANLG LOOP THD N test conditions AATHDTstCond str no ANLG LOOP Dynamic Range test conditions _ AADynRngTstCond Str Jo ANLG LOOP Signal to Noise Ratio test oe AG ANLG LOOP Crosstalk test conditions AAXtkTstCond Str Jo ANLG LOOP Max Pos Phase Error AAPhaseMax Str 0 000 deg ANLG LOOP Max Neg Phase Error AAPhaseMin Str itoo00 de ANLG LOOP Frequency Response ChB_____ AAResponse Dbl array fno eBv RC A e ANLG LOOP Frequency Response test ANLG LOOP Frequency Response Limit AARespLimit PC Audio Test User s Manual 99 Appendix B Results Listings MIC ANALOG LOOP A A Path Results MIC ANALOG LOOP A A Path Results Description Collection name Data Type Formatting Um le de Ren slider position MIC To o e ee Mic In Gain Maximum JAAMaxMicGain_ Str fH MIC LOOP THD N test conditions AAMicTHDTstCond fst no J MIC LOOP Dynamic Range test conditions AAMicDynRngTsiCond_ st ne J MIC LOOP Signal t
128. sam ple rates and resolutions for the modes requiring different multitone files Frequency response result levels are normally referenced to the result level at a mid range frequency usually 1 kHz For PC Audio Test frequency re sponse measurements the default reference frequency is 1 kHz You can enter a another value of your choice in the Frequency Response Reference Fre quency setting field 26 PC Audio Test User s Manual Test ID Chapter 2 Getting Ready Test ID Test Author Alan Smithie Company Symadrophone Division Cryonics Comments Works good Figure 27 The Test ID dialog box Double click on Test ID in the Test Explorer to open the Test ID dialog box The Test ID dialog box enables you to identify each test with an operator s name company name division and a comment The Test ID 1s specific to each test file as opposed to the User Information which persists throughout differ ent tests If you have entered User Information this information will appear as the default Test ID information for a New Test See User Information on page 27 User Information User Information E Operator Alan Smithie Company Name Symadrophone Division Name Cryogenics Unit Preferences Voltage Digital Amplitude ox Figure 28 The User Information dialog box PC Audio Test Users Manual 27 Chapter 2 Getting Ready User Infor
129. sing FFT techniques However the ripple component must be extracted from the raw response curve to create a useful plot and this is accomplished by FFT smoothing and then removing the converter response slope from the measurement using ana lyzer Compute functions Since the ripples in the passband appear in a linear relationship to fre quency the tones in the multitone stimulus are set in an approximately linear spacing The tones in the frequency response multitone are logrithmically spaced 6 dBr rec or at a level of your choice AES17 specifies the 1 dB stimulus level WHQL PC2001 specifies 3 dB The DUT ADC output is acquired directly within the PC and analyzed for THD N using FFT techniques Since the instrument Analog Analyzer cannot be used for this measurement the weighting or bandpass filters are not avail able for THD N measurements in the RECORD path In accordance with accepted practice for PC sound device measurements PC Audio Test expresses THD N results relative to the RECORD Level Ref erence rather than to the stimulus tone level Dynamic Range measurement See the Dynamic Range sidebar on page 48 For the RECORD path dynamic range measurement PC Audio Test applies E Dynamic a 997 Hz sine wave at a very low level to the Line Input jacks This tone is Range typically set to 60 dB relative to the DUT Analog Input Level l l l o lt ADDynRangA gt The DUT ADC output is acquired directly with
130. sing the DUT driver controls and monitoring the instrument control software dis plays Specific instruction for manual level setting in the PLAY ANALOG LOOP and RECORD measurement paths follow eal ADJUST PLAY D A MANUAL SLIDER SETTING Min Max 13 7240 Min Max 162 626 Last Measurement 0 01 0 02 005 01 0 2 9 ChanA 71 81 dBY THD 4 78 ChanB 41 69dBV THD 5 25 Adjust Play D A Manual Override slider control For maximum level and THD lt 1 Take a new measurement Headphone Speaker tes pc Audio Test Creative Sound Blaster PCI 1 y WE E a le Stetell Fie Edit View Tools Window Help C Mono SrA ILE gt 2 Test Explorer Source Analog Input na E Volume Control Options Help A SD Test ID BID PLAY D A Path i Volume Control 2 Level Reference C THD N Balance Balance C Dynamic Range LY Connection Assignments p Z p Ki C Frequency Response Audio Precision Hardware 1 O Passband Ripple DUT Instrument Switcher Volume Volume ANALOG LOOP A A Path Line or Spkr Out to BNC Unbal y 182 y i O Level Reference a O THD N Line In from Unbal Float x 1 amp 2 x AE O Dynamic Range Mic In from B
131. st Settings panel enables you to view and set specific measurement parameters and other test settings Double click on Test Settings to open the Test Settings dialog box The Test Settings dialog box enables you to make settings for each test The top section provides fields for setting sample rate and resolution for both Line In and Mic In recording 22 PC Audio Test User s Manual Test Settings Chapter 2 Getting Ready Each drop down list shows only the sample rates and resolutions available to the current DUT with the most common setting selected as a default Digital Settings DUT Converter Settings Sample Rate Resolution bits PLAY amp RECORD Line v RECORD Mic Level References Figure 22 Test Settings digital settings Set the sample rate Fs and resolution also called word length or bit depth for your test here In PC Audio Test the sample rate for the DUT s analog to digital converter ADC and digital to analog converter DAC must be set to the same value likewise the resolution for both the ADC and the DAC must be the same The selections made here set the sample rate and resolution for both the PLAY mode and the RECORD mode Some tests require that you set the sample rate or resolution when using Mic In to a different value from the Line In settings PC Audio Test enables you to specify sample rates and resolutions for both modes When performing a series of measurements that specify both Mi
132. t paths 1s set in the PLAY path measuring the analog output level when a digital file of known level is played m ANALOG LOOP Line In to Line Out A A This measurement path tests only the analog input and output circuits bypassing the analog to digital converter ADC and the DAC The line input is used for this path m MIC ANALOG LOOP Mic In to Line Out This measurement path is identical to the ANALOG LOOP mode except that it uses Mic In instead of Line In as the analog input m RECORD Line In Analog to Digital Recording A D PC This measurement path tests the analog input and the ADC using the line input m MIC RECORD Mic In Analog to Digital Recording A D PC This measurement path tests the analog input and the ADC using the mic input m RECORD PLAY Line In Analog to Digital Recording then Digital to Analog Playback of the file just recorded A D PC D A PC Audio Test User s Manual 35 Chapter 3 Running the Tests Running the Tests 36 This measurement path is a combination of the RECORD and PLAY paths using the line input m DIGITAL LOOP Digital In to Digital Out Pass Through This measurement path tests the digital interface receiver and transmitter with special digital tests that provide information about the DUT s handling of data and metadata Running the Tests m First be sure you have configured your DUT for PC Audio Test as discussed beginning on page 16 Run Ground Check m Chec
133. t User s Manual 3 Chapter 1 Introduction Basic Configurations Since digital to analog converters DACs often have high level out of band noise their performance can be more accurately measured when the ana lyzer bandwidth is restricted to the audio band by a filter Additionally stan dards or test requirements may specify a bandpass or weighting filter for certain measurements Option Filters Audio Precision manufactures a range of plug in filter modules called Op tion Filters which can be fitted in System Two including System Two Cas cade Cascade Plus and 2700 series instruments Band limiting low pass filters with a knee at about 20 kHz and A weighting CCIR and CCIR Dolby ARM filters are particularly useful in testing PC audio devices S AES17 Filter Audio Precision manufactures the S AES17 Filter which can be fitted in System Two System Two Cascade Cascade Plus and 2700 series instruments Unlike the Option filters the Audio Precision S AES17 Filter inserts a low pass filter section previous to the analyzer input reducing high level out of band signals before they can overload ranging or amplifier circuits Use of an S AES17 Filter is strongly recommended for PC audio device testing the PC Audio Test default configuration settings expect an installed S AES17 filter Basic Configurations APIB Connection Audio Precision Instrument Gro
134. t short circuited or with a specific value of resistance connected at the device input instead of a signal S PDIF Sony Philips Digital Interface a digital interface for consumer audio equipment Sometimes also referred to as the EIAJ interface The S PDIF is similar to the professional AES3 interface but is normally an unbal anced coaxial signal of lower amplitude Most of the status byte definitions are different between S PDIF and AES3 stimulus a known signal applied to an audio device under test chosen to stimulate device behavior useful for the test being performed THD N total harmonic distortion plus noise Measured by attenuating the fundamental signal with a narrow band notch filter then measuring the re maining signal which consists of harmonics of various order wide band noise and possibly interfering signals This is the common harmonic distortion method implemented in most analyzers third octave see one third octave unbalanced an audio connection in which the desired signal is present as a voltage with respect to ground or common rather than as a differential signal across a pair of balanced conductors weighting filter a filter with varying attenuation as a function of fre quency so as to produce a measurement where the various spectral compo nents affect the measurement 1n a specified fashion Most commonly used weighting filters are attempts to correspond to the varying response of the hu man h
135. the PC for DUT playback This signal is a 997 Hz sine wave at a standard level normally 0 dBFS See PLAY Level Reference Set tings on page 23 PC Audio Test sets the DUT playback mixer master volume slider to its maximum and adjusts the wave slider to find the step just below that which produces 1 40 dB THD N at the DUT outputs If the THD N is below 1 at any wave slider setting the wave slider is set to its maximum setting ee Level PC Audio Test then measures the signal voltages appearing at the DUT out Reference puts These voltages usually expressed in dBV units are used as the analog 38 PC Audio Test User s Manual PLAY Measurement Path voltage level references for all PC Audio Test measurements within a particu lar DUT These amplitudes are set as the instrument analyzer references O dBrypy ay A and B PC Audio Test refers to them as the PLAY Level References In PCAQM these references are called FSOV Full Scale Output Voltage for channels A and B Do PLAY Level Reference FIRST NOTE PLAY path Level Reference must be determined before any other measurements can be made Even if you are performing a reduced set of measurements for your DUT test you will find that PC Audio Test will always direct you to perform the PLAY path Level Reference measurement first Sample Rate Error The stimulus signal that is inserted into the DUT for PLAY Level Reference is produced by the instrument digital generator at pr
136. tude of the third harmonic is sufficient to characterize the distortion This third order harmonic or third harmonic dis tortion is expressed in relation to the stimulus signal as a percentage or ratio usually in decibels In other cases the total of the amplitudes of all the measured harmonics is required This total harmonic distortion or THD is expressed in relation to the stimulus signal as a percentage or ratio usually in decibels Since the re sidual noise of a device is usually at a very low amplitude compared to the dis tortion and is not easily removed from the results this measurement is generally performed to give total harmonic distortion plus noise or THD N Note that distortion is generally expressed as a ratio or percentage of the stimulus signal The standards that define PC audio device testing procedures however state the distortion as a ratio or percentage of 0 dBFS even if the stimulus has a lower amplitude This approach provides results that may be at variance with traditional distortion measurement techniques 44005 PC Audio Test User s Manual ANALOG LOOP Measurement Path Chapter 3 Running the Tests THD N measurement See the Distortion THD N sidebar on page 44 For the ANALOG LOOP THD N measurement PC Audio Test applies a 997 Hz sine wave to the Line In jacks Depending on your configuration set tings the stimulus level may be at 0 dB 1 dB 3 dB 6 dB or at a level of your choice
137. ual Chapter 4 Viewing and Reporting Results PC Audio Test provides test results as XML text Different sets of results may be saved as separate XML files The Results Viewer displays a dynamic HTML document that provides a formatted version of the current XML results data for viewing and reporting You can create custom HTML files to format the XML data for many different purposes The Results Viewer Choose View gt Results or click the Results Viewer button on the toolbar to open the Results Viewer File Edit view Tools Window Help xs Untitled Testi Test Settings Test ID Be PLAY D A Path BID Level Reference BID THD N BID Dynamic Range BID Frequency Response BID Passband Ripple BG ANALOG LOOP A A Path BID Level Reference BIO THD N BO Dynamic Range BAD Frequency Response BID crosstalk BS mic ANALOG LOOP A A Path BID Level Reference RO THD N BAD Dynamic Range BID Frequency Response a BIO rec A D Path BID Level Reference BIO THD N BID Dynamic Range BID Frequency Response EID PassBand Ripple BS a sal gt nal a Creative Sound Blaster PCI Pp Creative Sound Blaster PCI 1 IB SoundMAX Digital Audio amp SoundMAX Digital Audio 1 Test Results ES EN PC Audio Test Results a Detailed Test Results PLAY ANALOG MIC RECORD REC PLAY DIGITA Device and Test Information Device Under Test Model Serial Number Operator name Operator company
138. uded with PC Audio Test to help you get started quickly and to be sure that you have a proper interface two unbalanced shielded standard audio cables fitted with BNC connectors and 3 5 mm TRS plugs one Mic Bias cable fitted with one male and one female XLR con nector and a 3 5 mm TRS plug and a grounding cable The three audio cables are color coded to correspond to the standard recom mended identifying colors used for PC card and motherboard audio jacks m lime green should be connected to the PC audio device line inputs m light blue should be connected to the PC audio device line outputs or speaker connections depending on the device and your test goals m pink should be connected to the PC audio device mic input for most PC audio devices 12 PC Audio Test User s Manual Getting Ready This chapter discusses software installation and the interconnections and configuration necessary to set up a PC audio test We recommend that you read this chapter carefully and that your first test be designed for a local sound device one mounted in the same PC that is controlling your Audio Precision instrument Local testing is described in Chapter 3 If you are testing a PC au dio device mounted in a remote client PC refer to the DCOM information in Chapter 5 after you have mastered local configuration and testing Installing the Software m Close all applications m Insert the APP 2010 PC Audio Test disk into the CD ROM drive
139. und Connection Local Computer with DUT Figure 2 Local test configuration Figure 2 shows a typical PC Audio Test local test configuration An Au dio Precision instrument is connected to a PC that has both the instrument con trol software and PC Audio Test installed Audio connections are made between the instrument and the sound device under test or DUT mounted in the PC A PC Audio Test User s Manual Basic Configurations Chapter 1 Introduction Network Connection APIB Connection Remote Computer with DUT Audio Precision Instrument Ground Connection Figure 3 Remote test configuration Local Computer Figure 3 shows a typical remote test configuration In this case the instru ment control software and PC Audio Test are installed in the host computer which controls the instrument and runs the tests The DUT hardware and a second instance of PC Audio Test are installed in the client computer A net work connection is shown between the two computers to enable remote opera tion using Microsoft Window s DCOM facility PC Audio Test User s Manual 5 Chapter 1 Introduction Quick Tour Quick Tour The next few pages will give you a quick tour of the PC Audio Test features and interface Detailed information 1s provided 1n later chapters and referenced from the Quick Tour topics See Chapter 2 for s
140. urement As you raise the level there will usually be a threshold at which the distortion in PC Audio Test User s Manual 81 Appendix A Troubleshooting Test Failures 82 creases greatly set the level just below this point Then continue with your test NOTE You may notice high distortion readings at very low control settings while making these settings The ranging of the instrument input circuits will amplify system noise under conditions of very low signal and the noise reading will be expressed as a distortion reading Manual ANALOG LOOP level control setting See ANALOG LOOP Measurement Path on page 42 for reference PC Audio Test s ANALOG LOOP Reference Level algorithm attempts to find the correct analog 1n to out operating level for the DUT by searching for the maximum generator setting and Line In playback slider control level that produces less than 1 distortion THD N at the Line or Speaker output To locate the optimal level manually first open the DUT Playback mixer and set the Master Volume and the analog input volume usually the Line In control to their maximum In PC Audio Test click Run The following dialog box will open Manual Line In A A slider and Generator Amplitude A 24 y Last Measurement Chan 4 48 dBY THD 0 01 ChanB 4 72dBY THD 0 01 IF Distortion is high and Level low reduce Generator output If Level and Distortion are low increase Input 4 4 Manual Override slider co
141. urements For the instrument generator the reference is the same for both output channels and is designate dBr PC Audio Test calls this reference dBr reo For the instrument analyzer there is a reference for each input channel dBr A and dBr B PC Audio Test calls these references dBr pray For PC Audio Test measurements the voltage level measured in the PLAY mode level reference measurement defines 0 dBr for all the other measure ments within the test Once defined by the level reference measurement then O dBFS 0 dBr pray Unity Gain forces the ANALOG LOOP measurements to be performed un der the assumption that a given input voltage at a channel line input will pro duce the same voltage at the channel line output and that the DUT is designed to accommodate unity gain operation with good performance at a reasonable mixer slider volume setting Level Reference with Unity Gain selected default To establish the ANALOG LOOP Level Reference PC Audio Test applies a 997 Hz sine wave to the DUT Line Input at the voltage that corresponds to 20 dBr Aray The playback mixer Line In volume slider is adjusted until the voltage at the Line Out A jack is the same 20 dBr Apr ayy NOTE The step resolution of mixer sliders is often coarse and it is usually not possible to adjust the slider so that the Line Out voltage exactly equals the Line In voltage PC Audio Test finds the slider setting that produces the closest result a
142. ust be determined before any other mea surements involving the Mic inputs MIC RECORD RECORD PLAY LOOP with Mic input can be made Mic In Recording Slider setting PC Audio Test reads the recording mixer Mic In slider position at MIC RECORD Level Reference The position is reported as a step number See the Slider Position sidebar on page 41 THD N measurement See the Distortion THD N sidebar on page 44 For the MIC RECORD THD N measurement PC Audio Test applies a 997 Hz sine wave to the DUT Mic Input at a nominal amplitude The THD N stimulus is always a 997 Hz sine wave Depending on your configuration set tings the stimulus level may be at O dBr rec 1 dBr rec 3 dBr Rec 6 dBr rec or at a level of your choice AES17 specifies the 1 dB stimulus level WHQL PC2001 specifies 3 dB For MIC RECORD 0 dBr is generally much lower on the order of 30 dB to 40 dB lower than the O dBr established for Line In The DUT ADC output 1s acquired directly within the PC and analyzed for THD N using FFT techniques Since the instrument Analog Analyzer cannot be used for this measurement the weighting or bandpass filters are not avail able for THD N measurements in the MIC RECORD path In accordance with accepted practice for PC sound device measurements PC Audio Test expresses THD N results relative to the MIC RECORD Level Reference 0 dBr rather than to the stimulus tone level Dynamic Range measurement See the
143. ware In PC Audio Test use it means that the THD N or Dynamic Range filter specified in your Test Set tings is not installed in the Audio Precision instrument ERROR Test Failed No Data or Sweep Timed Out Signal may have been interrupted The above message can apply to any test Configuration is correct but mea surement failed This is usually a connection problem such as cable not con nected or connected to the wrong DUT or instrument port For frequency response crosstalk or passband ripple tests which use multitone measure ments a high level of DUT glitching can cause this failure ERROR Test Failed Max Min Compute failed Signal may have been interrupted The above message applies to frequency and phase sweeps The data ac quired for computation may be corrupted Try re running the test PC Audio Test User s Manual 85 Appendix A Troubleshooting Test Messages 86 ERROR Chan A and or Chan B signal below 20 dBV Check Connections and DUT Properties Configuration Messages like the one above can appear at various places within the mea surement procedure The specified level here shown as 20 dBV may be dif ferent depending on the test requirement This message usually means there 1s no signal which points to a connection problem a DUT or instrument config uration problem or an extra DUT software driver mixer control that is not enabled ERROR Frequency not within 1 of 997 Hz
144. xer with a volume control for this path usually called the Line In slider control Other recording sliders may be provided but in most cases the recording multiplexer allows selection of only one at a time In some DUTs the recording multiplexer Line In volume and the playback mixer Line In vol ume are addressed by the same slider control Frequency Response Frequency response is one of the most common and telling audio measure ments Conventional frequency response measurements use as a stimulus a se ries of single frequency tones spaced across the passband or a continuous sweep of frequencies swept from one end of the passband to the other The out put of the DUT is measured at each frequency of interest and the level mea sured is plotted against frequency to produce as response graph or curve The maximum deviations are commonly measured from a nominal mid band fre quency often 1 kHz and the response is given as a graph or as a statement of deviation such as 2 dB 20 Hz 20 kHz Audio Precision uses an alternative multitone technique for PC Audio Test frequency response and passband ripple response measurements In a multitone measurement a special stimulus signal is created in digital signal processing that contains all the frequencies of interest at precisely known lev els and frequencies This signal is applied as an analog or digital signal as necessary to the DUT and the output of the DUT is analyzed using FFT tech
145. y Test Settings Test Settings By default PC Audio Test characterizes a sound device under test DUT with a full suite of measurements performing level checks noise distortion and frequency response measurements on the DUT through all the signal path modes available In many cases however you may want to specify certain measurement pa rameters or run only a subset of the whole suite of measurements The Test Explorer and the Test Settings panel enable you to customize your choice of modes measurements and setups Both Test Explorer settings and Test settings can be saved and reloaded as a PC Audio Test file which uses the filename extension set The Test Settings dialog box YD Test Settine B DUT Converter Settings Sample Rate Resolution bits PLAY 8 RECORD Line 48 00kH2 RECORD Mic 24 00kH2 m 16 fm Level References Play D A O dBFS w 0 dBr P 4 4 Unity Gain Record 4 D OdBr R OdBFS y C Mic Boost On THD N Stimulus Level 3 dB w Below Reference Level Filters 20kHz AES17 M Filters marked must be installed Dynamic Range Stimulus Level 60 dB Below Reference Level Filters 20kH2 AES17 M Filters marked must be installed Frequency Response Stimulus Test File Response Ref way and agm Freq O dB at Line 48kHiResFregResp M 1 kHz iv Mic 24kHiResFregResp M Figure 21 The Test Settings dialog box The Te
146. y switch the connections between the instrument and the DUTs You can also use a switcher to automatically select Mic In or Line In con nections in some configurations PC Audio Test User s Manual Using a Switcher Appendix C Connector Designations Audio Precision manufactures input and output switchers that can route many inputs and outputs to and from the instrument generator and analyzer under the control of PC Audio Test PC Audio Test User s Manual 111 Appendix C Connector Designations Using a Switcher 112 PC Audio Test User s Manual Appendix D Glossary A A PCAQM PC2001 abbreviation for Analog Analog measurement path Commonly referred to in PC Audio Test as the ANALOG LOOP mea surement path A weighting A weighting filter see weighting filter ADC see analog to digital converter A D PC PCAQM PC2001 abbreviation for Analog Digital Personal Computer measurement path Commonly referred to in PC Audio Test as the RECORD measurement path A D PC D A PCAQM PC2001 abbreviation for Analog Digital Personal Computer Digital Analog measurement path Commonly referred to in PC Au dio Test as the RECORD PLAY LOOP measurement path AES the Audio Engineering Society with headquarters in New York City AKS3 interface a digital interface standard for professional audio equip ment interconnection defined in the AES3 standard Formerly known as the AES EBU interface The digital signal carried in the

User`s Manual - waynejones.net

Contents

Download Pdf Manuals

Related Search

Related Contents