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User Manual A2

1. Warbled Sine Frequency Readback Output Muting Overview Display Modes rrer 6 104 om Eii V3 1 A2 Audio Test amp Measurement System User Manual Generator SOMOS oree eE E EE S sa snd EE EE A Sea E E EEEo 35 Generator Readback 35 Measurement Results 35 The Bar graph Zooming the Bar graph Scale Scrolling the Bar graph Input Display i Printouts GRAPH Display Mode Y Scaling 39 ZOOM 39 SCROLL 40 X Scaling 40 Store amp Recall Graphs SCOPE Display Mode Printouts Overview 5 MEASUREMENT FUNCTIONS Level Function ccecsceeees we 44 Mono Stereo Measurements Units Filters Applications Overview Level Relative Function Filters Units 48 Application Example 48 Signal to Noise Measurement THD N Function Notch Filter Additional Filters Units Filters Applications Noise Relative Function Units Filters Crosstalk Function Units Filters External Source Level Selective Function Filters Prey V3 1 om 7 104 User Manual A2 Audio Test amp Measurement System External SOUnCG a coc sscewects ET T E E N 62 Units wee Applications Wow amp Flutter Function Standards W amp F Measurements Replay only W amp F Measurements Record to R
2. This is done by setting the generator to the required start value in Frequency mode the start frequency in Amplitude mode the start level and pressing the lt START VALUE gt button Consequently the A2 A2 D accepts the current generator frequency level value as start value and re scales the Xaxis of the graph To define the stop value proceed the same way but press the lt STOP VALUE gt button Con sequently the X axis will show the user defined sweep range NOTE The start value doesn t need to be lower than the stop value it is also possible to sweep from a higher to a lower frequency level by setting the start amp stop values accordingly Nevertheless the x axis will always drawn in increasing order from left to right even if the sweep is per formed in the other direction The resolution of the sweep can be set to two stati either LOW or HIGH High resolution sweeps are performed if the accuracy is important while the low resolution is chosen if speed is the major issue Low igh The number of points can be altered by the user for both set tings by double clicking the lt RESOLUTION gt key in the corre 1m sponding status This will open the Resolution menu showing the actual number Low Resolution of points Turn the lt SCALE gt wheel to increase or decrease the number and push the wheel to confirm the selection 30 Pts Sweep The table below lists the possible ranges of the LOW HIGH resol
3. User Manual The A2 A2 D allows to install weighting filter s on the main or both input channels The available filter characteristics are e the standard Aweighting filter AQ4 e a customer specific filter AO5 e the C Message weighting filter AO13 or e the 80kHz lowpass filter AO14 A Weighting Filter AO4 Frequency Hz Gain dB Frequency Hz Gain dB Frequency Hz Gain dB 20 50 5 200 10 9 2000 1 2 25 44 7 250 8 6 2500 1 3 31 5 39 4 315 6 6 3150 1 2 40 34 6 400 4 8 4000 1 0 50 30 2 500 3 2 5000 0 5 63 26 2 630 1 9 6300 0 1 80 22 5 800 0 8 8000 1 1 100 19 1 1000 0 10000 2 5 125 16 1 1250 0 6 12500 4 3 160 13 4 1600 1 0 16000 6 6 20000 9 3 5 q 10 gt 15 20 5 30 35 40 45 40 100 1k 10k Frequency Hz Fig 26 A Weighting Filter Characteristics V3 1 91 104 User Manual A2 Audio Test amp Measurement System User Filter AO5 The user filter comprises a PCB with four operational amplifiers and the switching electronic to enable and disable the filter s The space around these devices is reserved to add passive components like resistors and capacitors thus allowing to deaign a custom specific filter characteristic Possible applications of the User filter are e Fixed lowpass filter with 80dB decade 24dB octave at any frequency e Fixed highpass filter with 80dB de
4. surement functions lay modes Me Disp Input section o 0 c eaL8 m A2 Audio Test amp Measurement System Generator control Display section Output section 18 104 T bie BG V3 1 nti docTest amp Measurement System User Manual A2 A2 D Menu Overview a Gen Blabus bi Tove Bisplay th a ta d 5 ZS Bet toe EX EXT Serer heal Q 19 9dBu GEN 26 20 Hz p id o Ca AD am a am om IMD Icsl ig Unite Solan Pisk Noise Martla DTT vat ine rs 19 104 _nti doc Test amp Measurement System This page must not be inserted in the manual V3 1 rr Li iiii A2 Audio Test amp Measurement System User Manual 4 A2 A2 D OPERATION NOTE Before switching On your A2 A2 D make sure that the selected mains power voltage matches the one of your area If not please refer to chap ter 2 Installation to set it correctly Each time the A2 A2 D is switched On it performs a short self test during which the A2 logo will be displayed together with the software version the current time setting of the internal clock and the serial number ofthe unit After this test the A2 A2 D will present itself in the last active setup i e show the same set tings and selections as when it was switched off Nevertheless it is also possible to define and recall a user setup see chapter Store amp Recall Setups
5. 71 104 User Manual A2 Audio Test amp Measurement System Table 6 Minimum No of Recordable Sweep Curves To recall a stored graph open the Graphics menu and select one of the Recall Mx menu entries This process also re activates the instrument setup that was active when the graph was saved Recalling a graph does not clear the corresponding memory When moving the arrow along the Recall Mx entries the bottom line of the LC display shows the stored time amp date of the graph stored therein If no graph has been stored in the corre sponding memory location NO DATA is shown instead This feature simplifies the identifac tion of stored graphs NOTE When recalling a graph the actual graph on the display will be overwrit ten As soon as a graph has beeen recalled additional traces may be recorded and added The only limitations are given by the number of recordable traces and the measurement function that must not be changed In other terms if the measurement function is changed after having recorded one or more sweeps all displayed curves will be deleted Nevertheless previously stored graphs are not affected by this rre 72 104 on Eii V3 1 A2 Audio Test amp Measurement System User Manual Sweep Modes Frequency Sweep The most common sweep type is the internal frequency sweep where the frequency is the variable sweep parameter generated by the A2 A2 D This sweep type is best suitable for DUTs that don t
6. Print bi directional OFF Baudrate not used 10cpi OFF Hyphenate 10cpi OFF Auto LF hp Laserjet Deskjet No settings required All printers with PCL3 or PCL5 language may be controlled in this mode This covers almost all HP printers including the color printer types that support black amp white printouts Printer Error In case that it is not possible to properly communicate with the printer an error message will appear on the LC display of the A2 A2 D Prey V3 1 om 83 104 User Manual A2 Audio Test amp Measurement System Printer ERROR or no printer connected The reason for this message may be one of the following e Printer not connected to the CENTRONICS parallel interface of the A2 A2 D e Printer is switched OFF e Printer is Offline e No paper in the printer Any keypress to the A2 A2 D2 lets the error message disappear and return b normal operation rre 84 104 on Eii V3 1 A2 Audio Test amp Measurement System User Manual 8 INSTRUMENT SETUP Store amp Recall Setups The A2 A2 D stores its actual setup when it is switched off This means that after the next power up the instrument automatically resumes with the same settings Furthermore the A2 A2 D offers the possibility to store another setup in an internal non volatile memory location The s tored parameters are the actual e display mode e measurement function e filter s e generator settings e s
7. Recall Setups siirre eaea aeai eaaa aiaia 85 Calibration Connector Pin Assignment Centronics Connector rreo 8 104 Eii Eii V3 1 A2 Audio Test amp Measurement System User Manual Timing Diagram RS232 Connector 9 OPTIONS amp ACCESSORIES ccccccsesssccseseeceeseeecesaeeecseneeeessaeeeessaeeeessaeaeensneaess 89 Options Overview RS232 Serial Interface AO1 AO16 Baudrate Selection Filter Options A Weighting Filter AO4 User Filter AOS5 C Message Filter AO13 z 80kHz Lowpass Filter A014 94 Transformer Option AO7 Phantom Power AO8 Accessories OvervieW tssscsennroro cna aie aan Oa ae eee 10 TECHNICAL SPECIFICATIONS cccccscccssseessecesseecssecseeecseeeeseessaeecsatesseeeeseessaes 96 Analog Generatoriai unaia ist Dect casos cen ae A aE EEOAE tech Ea cae ehieels 96 Digital Generatoi sscan aenea Adena EE EEEE EEEE ati 96 Sweep Function Analog Analyzer Digital Analyzer Level Function Total Harmonic Distortion THD N Frequency Function SCOPE FUNC ON resect nists ninaa cots ea a N ta sree tae ASA EN e enna Filters Display of A2 A2 D Interfaces General Data MINDE Xr et oN A E ee pippe V3 1 om 9 104 User Manual A2 Audio Test amp Measurement System 1 INTRODUCTION Safety Information Please read this safety information thoroughly before starting to operate the A2 e The NTI A2 A2 D Audi
8. aia Oo If necessary one may tilt the instrument j N ae slightly either by turning the carrying handle j ED E gt below the underside or use the reversible lt T footings in order to optimze the view on the ats ue Mime 430a a G LCD x A AR Aue Furthermore you may adjust the contrast of D 8 mmea the LC display to your demands by turning the potentiometer wheel on the left hand side Set contrast rs The A2 A2 D is equipped with a screen saver function to extend the lifetime of the LCD backlight The backlight darkens after 10 minutes without any operator activity To turn it On again simply press any key or softwheel Input Section The A2 A2 D is a two channel measurement system providing two fully independent meas urement channels named MAIN and ALTERNATE Both channels are equipped with an in put impedance circuitry input attenuators amplifiers and a filter bank This allows e g to measure weighted or unweighted levels of both channels simultaneously Additionally the main channel analyzer is equipped with a special filter section for Harmonic Distortion Intermodulation and Noise measurements and also provides the demodulator and filtering for W amp F measurements The lt A B gt key allows to select which of the input connectors shall be the main channel of the instrument In other terms the input signal of the illuminated i e active channel is al ways fed to the main channel while the other input sig
9. covered by this warranty NTIAG Neutrik Test Instruments Im alten Riet 102 FL 9494 Schaan Principality of Liechtenstein Europe Tel 423 239 6060 Fax 423 239 6089 E mail info nt instruments com Prey V3 1 om 5 104 User Manual A2 Audio Test amp Measurement System TABLE OF CONTENTS 1s INTRODUCTION gorscn urnie anti eetan aa 10 Safety Information Overview How to use this Manual 2 INSTALLATION E E Unpacking iec ene anea eieaa aean AEAEE EAER EAEE AE a SAESAARE EEEE EEEE Options and Accessories Environmental Conditions Mains Power Supply Printer Connection Interface to PC 3 GETTING STARTE D seeria enanar eieaa aE ea EEEren E RAEE EREE ese 15 Measurement FUNCHONG rescssninonionoruia cca een eee a EEEE Ie 15 Menu Operation Generator Settings The Display Modes Sweep Operation The A2 A2 D User Interface A2 A2 D Menu Overview 4 A2 A2 D OPERATION Input Section Input Block Diagram Input Wiring amp Impedances Input Output Impedance Selection Auto Fixed Range 2 eee eee Connection of a Balanced Output to the A2 A2D Connection of an Unbalanced Output to the A2 A2 D Monitor Outputs Monitor Loudspeaker Overview Output Section Output Circuit Balanced Operation Unbalanced Operation Optional Transformer Output Stage Output Settings Output Parameter Signal Waveform Square Signal Sym A IMD TestSig Noise
10. every display mode through the CENTRONICS interface by pushing the lt PRINT gt button Various printer drivers as e g Epson FX 80 LQ 1000 HP Thinkjet HP Deskjet Laserjet and IBM Proprinter are available The CENTRONICS printer interface is located on the rear panel of the A2 A2 D It is a 25 pin D type connector of the same type as in PC compatible computers Printer Driver Selection The A2 A2 D is very flexible and capable to drive a wide variety of different printers Actually following printer types are supported e IBM Proprinters and its compatibles e EPSON FX80 and its compatibles e EPSON LQ 1000 and its compatibles e HP Thinkjet e HP Deskjets HP Laserjet PCL3 and PCL5 language In case that your actual printer is not listed in this survey refer to the user manual of your printer for possible emulation modes Almost all printers may emulate at least one of the types as listed above If in doubt please contact your local printer supplier a To select the printer driver of your choice open the Printer Type menu by double clicking the lt PRINT gt button i j The menu offers the list of available printers Move the arrow Printer Type On the left hand side by turning the lt SCALE gt softwheel and IBM Proprinter place it besides the required printer driver Confirm the Epson 101000 selection by pushing the lt SCALE gt wheel once The two last menu entries Do FormFeed and RESET Printer hP
11. 20Hz 20kHz in 50s w o 1kHz header e PHILIPS Audio Signals disc 1 Track 6 20HZ 20kHz in 120s w o 1kHz header Pro Ty 78 104 om Eii V3 1 A2 Audio Test amp Measurement System User Manual Amplitude Sweep The A2 A2 D is capable of performing amplitude sweeps in all measurement functions Again in some measurement functions the variation of the level does not have a big influence on the result which simply is not of interest e g a W amp F sweep over the amplitude does not expect any variation Sweep Move ee EXT Activate the Sweepmode menu by double clicking the lt SWEEP MODE gt button The menu will appear Move the arrow with the Sra SCALE wheel to the entry Amplitude and push the lt SCALE gt wheel The menu closes automatically after the selection EX T Sweepmode or any other keypress leaves the menu without changes As soon as you enter the GRAPH display mode you will find the X scale as an amplitude range now The settings for the sweep range is done exactly the same way except that the generator lt LEVEL gt wheel is now used for the selection Units of X Y axis The unit of the X axis may be either linear V or logarithmic dBV dBu or dBm while the unit of the Y axis must be set in the respective measurement function 1 Select the amplitude sweep mode as described above 2 Activate the measurement function Level or 2 CH and choose the unit for the X axis V dBV dBu dBm by pressing t
12. B gt key Both in the 2 channel Level and Phase measurement function the two input signals are shown in a true phase position In the THD N function there are also two traces displayed the smaller one is the distortion residual after filtering out of the fundamental frequency while the larger trace shows the un filtered input signal Both traces are synchronized to enable inspection of where the distortion is occurring Be ware though due to the phase shift of the notchfilter which removes the fundamental fre quency that the distortion products cannot be exactly synchronized This effect is worst with the second harmonic In the Noise measurement function the SCOPE mode is blocked in a way that the A2 A2 D automatically switches its display to the METER mode ta ae oe 42 104 Eii Eii V3 1 A2 Audio Test amp Measurement System User Manual NOTE The SCOPE mode is blocked in measurement function Noise by switching the A2 A2 D display automatically to the METER mode This is because there would be no signal but some flickering dots visible only The display can also be frozen to analyze moving signals by a second push to the lt SCOPE gt button The message STORED is then displayed to indicate the frozen state Another push to the lt SCOPE gt button releases this state Printouts Like all other display modes the SCOPE display can be printed out to a Printer by pressing the lt PRINT gt key During the prin
13. Fix on the second line on the METER display reads np 200 Inp 150 EXIT or Phantom NOTE If the Phantom power option is installed the 200Q 150 input imped ance is not available TETI V3 1 om 23 104 User Manual A2 Audio Test amp Measurement System Auto Fixed Range The menu behind the lt A B gt key allows you to choose between the Auto and Fixed range setting In the Auto range mode i e the normal mode the operator never has to worry about the settings of the input amplifiers However for some applications like testing short bursts it might be helpful to lock the ampli fiers in a certain state AIB The Fixed range selection locks the input attenuators amplifiers in their actual state as soon as it is chosen by a push on the E lt SCALE gt softwheel Range Ranging 7 If the input signal level is under or over the actual Fixed range gt ET aaa then the messages TOO LOW or TOO HIGH will appear on the Fixed LCD instead of a measurement result EXIT To lock the input attenuators amplifiers to a fixed range proceed as follows e Apply the input signal to which you want to adjust the ranging e Call the Ranging menu by double clicking to the lt A B gt button e Select the entry Fixed by positioning the arrow through the lt SCALE gt wheel Push the wheel once to activate the setting the menu closes automatically The input stages are now fixed and all measurements will be performed in
14. The LCD will show one measurement of Wow amp Flutter in big digits and one of Drift on the bottom line both as a percentage The wow amp flutter result will also be shown on the bar graph 4 If the input level from the recorder is too low the message INP LOWwill appear NOTE The A2 does not strictly measure drift but rather speed error Drift is the difference in speed between the beginning and end of a tape or disc Therefore to measure drift you will need to take two measurements one near the beginning and one near the end and subtract one from the other Be careful if one has a positive and the other a negative result W amp F Measurements Record to Replay The procedure is basically the same as before except that the blank tape has to be recorded first To do this proceed as follows 1 Connect the generator output of the A2 A2 D to the record input of the recorder 2 Load a blank tape 3 Start the tape machine in the record mode 4 After a suitable length of recording usually at least 30 seconds rewind the tape and restart in the replay mode tia a oe 64 104 om Eii V3 1 A2 Audio Test amp Measurement System User Manual NOTE Don t measure wow and flutter whilst actually performing the recording because W amp F at some frequencies will be canceled out and the meas urement will be lower than the truth Frequencies which will be canceled are those where the delay from the record hea
15. also Fig 7 Muted outputs result ina as very quiet output being properly terminated with C N the selected impedance This feature simplifies output measurements of a re DUT that is not stimulated with any signal by making the physical disconnection of the gen um w erator obsolete Overview The generator outputs may be operated either balanced or unbalanced The selectable output signal parameters are the waveform frequency and level To set the output impedance use the lt IMPEDANCE gt menu key In the METER mode the output voltage or impedance may be displayed The generator outputs may be mutes by pressing the respective lt MUTE gt keys User Manual A2 Audio Test amp Measurement System Display Modes Depending on the type of information you need the A2 A2 D offers three different display modes e The METER panel for single measurements e the GRAPH mode for sweep recordings and e the SCOPE mode to watch the time signal GEN 1 kHz 14 SdBu ae Es a E 2 CHN coe 5 55dBu ea pe ce 14 4dBu Ais Titi ty 5 STU E ieo 5 550 Eie 14 408u Fig 10 METER Mode Fig 11 GRAPH Mode Fig 12 SCOPE Mode NOTE Regardless of the active measurement including sweeps it is always possible to switch to any other display mode without compromising the accuracy of the measurement METER Display Mode This display mode is entered by pressing the lt METER gt key once It provides al
16. amp Measurement System User Manual Level Selective Function The Level Selective measurement function measures the RMS level of the input signal but by applying a narrow bandpass filter to analyze a small frequency band only To enter the Level Selective measurement function press the lt L SEL gt button one or two times so that the LCD shows L SEL Each further press to the button toggles the meas urement mode of the A2 A2 D between XTALK and L SEL IND NREL A t Akire DAPLAY MODE mir a D R Filters In L SEL mode the displayed result equals the RMS energy content of the signal measured behind a narrow bandpass filter This filter is of 2nd order with Q 5 and a constant relative bandwidth This means that the filter characteristic has the same shape if plotted vs a loga rithmic scale regardless of the actual frequency to which it is set The characteristic of the narrow BP filter is the same as plotted in chapter Crosstalk Function p 59 This filter type has the advantage of being tunable over the whole Audio range up to 50k z and of having a constant Q factor over the entire frequency range With its constant relative bandwidth the energy content of white noise under the filter is not constant but increases with 10dB decade For instance the thermal noise of electronic devices typically shows a linear distribution i e very similar to white noise Therefore if analyzed w
17. and dBr e Frequency two channels simultaneously e Phase interchannel in the range of 180 In the METER display mode all measurement results are displayed in numerical form as large digits and in analog form through a bar graph Additional parameters like the 1 0 frequencies and impedances the input levels and the generator settings are permantly shown aaa ae 10 104 om Eii V3 1 A2 Audio Test amp Measurement System User Manual The standard sweep capabilities of the A2 A2 D allow to perform e Frequency sweeps e Amplitude Sweeps e Time Sweeps e Table sweeps with freely definable pairs of frequency and level with Option AO1 Sweeps can be controlled by the builtin generator or by an external source e g test tapes test CDs or other NTI Aseries instruments at a remote location Several traces can be recorded and displayed in the GRAPH mode while up to four complete graphs may be stored in the internal non volatile memory of the A2 A2 D This allows for instance to record swept measurements in a studio and to print out the results in the office later Another powerful diagnostic aid of the A2 is the SCOPE function In this mode the waveform of both input channels is shown on the LC display just like on a dual trace oscilloscope If set to the THD N function the A2 A2 D shows both the original signal and the distortion residual In other measurement functions the main input signal is shown as a single trace All
18. and press the lt SCALE gt Alt Signal wheel once Square 5 Consequently the actual selection of the alternate signal will gt a cacti change accordingly i e the new signal will become active and IMD TestSig the menu will close automatically White Noise Pink Noise Alternatively selection of the EX T entry or any keypress to the Warble A2 A2 D keyboard will leave the menu without a change of the EXIT actual setting In some measurement functions ike IMD and W amp F a predefined wave form depending on the selected standard is activated as alternate sig nal Pre Ty V3 1 om 29 104 User Manual A2 Audio Test amp Measurement System Therefore activation of the Alt Signal menu will show this setting Al though it is possible in this state to alter the signal in the me nu it will be re set automatically to the predefined waveform as soon as the menu is closed Square Signal Sym Asym The Square Sym and Square Asym are squarewave signals with either a duty cycle of 50 50 ym or 40 60 asym Regardless of the duty cycle the squarewave signal has the actually selected frequency and level calibrated in true Vrms A typical application for the 40 60 signal may be for quickly checking the polarity of lines IMD TestSig The IMD test signal consists of two signals components e a sinewave with a fixed frequency of 60Hz or 250Hz and e a second sinewave with a frequency of at least 4kHz that m
19. and the timing of the CENTRONICS port Interface to PC Connection The RS232C serial or IEEE 488 parallel interface is available as an option together with the software package AS04 to control the A2 A2 D as a remote unit As long as this interface is not installed the hole for the connector is covered with a blanking plate Both interface types can be upgraded at a later time by inserting a sub circuit Please refer to the chapter 8 Instrument Setup for more detailed information ccccocsevnee E TM 01234567 Centronics Printer Port Fig 1 Rear Panel Interface Connectors Ppt 14 104 on V3 1 A2 Audio Test amp Measurement System User Manual 3 GETTING STARTED Read this chapter carefully to become familiar with the operation of the A2 A2 D Further details are filed in the following chapters The NTI A2 A2 D system is very easy to operate despite its large number of functions and the variety of options amp settings Since the user interface is arranged in logical blocks and every key correlated to a certain function operation of the unit is virtually self explaining Nevertheless regardless of the keys that are pressed the internal logic of the system takes care that every measurement is done according to the specified standards Measurement Functions The measurement related keys are arranged on the top row of the right hand side of the A2 A2 D keyboard Any measurement function may be selected
20. at any time by pressing the respective key LEVEL TH2 h Wa NOSE SROZETALK PHASE eS es eo Ro wn NRT sa ARIT ONAL Fig 2 Measurement Function Keys Some of the keys provide two selections thus allowing to select another related measurement e g lt THD N gt and lt IMD gt To activate he second function simply press the key once more and the measurement mode will toggle The actually selected function is permanently displayed Menu Operation To allow the user to activate a special option or setup several menus may be opened by double clicking any of the keys marked with a capital M in the bottom right seep 19 SEN SON As soon as the menu is open a list of selections appears with the currently active selection being displayed in inverted i characters In this example by double clicking the lt GEN SIGNAL gt key m Alt Signal p the Alt Signal menu appears Square 5 F F To change the actual setting the small triangle arrow on the imaquare Asya i left hand side may be moved to any entry of the menu b IMD TestSig y y Ey y Tri 1 turning the lt SCALE gt wheel To confirm the chosen entry white Noise press the lt SCALE gt wheel once Pink Noise If a new selection has been confirmed the menu will be bees closed Alternatively leave the menu through the EX T entry or by prressing any key v3 1 HTE 15 104 User Manual A2 Audio Test amp Measurement System N
21. gt le 3 HE P Si i wy tor H ran fi d ALTONA ITP APARATO TT APR TOAD Lauth Hl a z L zf at At Fig 19 Principle of THD N Measurement WEADUREWENT INGTON To enter the THD N measurement func ye iii tion press the lt THD N gt key This button toggles between the measurement func e E ED tion THD N and IMD REL NREL OL Da NOTE Activation of the THD N measurement function automatically selects the sine signalas output for the A2 A2 D generator At the same time the notch filter is inserted into the signal path and the THD N value is calculated according to Equation 1 Distortion Noise Signal Distortion Noise Equation 1 THD N Calculation THD N NOTE If the level of the input signal is too low or not present at all the mes sage INP LOW will appear on the METER display FETI V3 1 om 49 104 User Manual A2 Audio Test amp Measurement System Notch Filter To control of the center frequency of the notch filter proceed in either of the two ways de scribed below 1 Lock the center frequency of the filter to the generator output frequency 2 Let the center frequency synchronize to the dominant frequency of the input signal Controlling the filter internally by the generator allows the filter settle in the quickest way This helps to speed up sweeps but requires the internal generator as signal source Furthermore the DUT must not produce a frequenc
22. measurement is performed by inserting a narrow bandpass filter into the analyzer path To measure the Crosstalk connect the generator outputs of the A2 A2 D with the inputs of the device under test DUT and the two output lines of the DUT with the input channels A and B of the A2 A2 D Then press the lt CROSSTALK gt button once so that the display will show XTALK Each fur ther push toggles the function between XTALK and L SEL MANEI HIN ws IND m DAY A DES piss N ye i Atirni i y gt R The generator output of the active analyzer channel is automatically muted in order to sim plify the Crosstalk measurement Furthermore the selective bandpass filter is inserted auto matically into the analyzer path of the active channel and tuned to the oscillator frequency The frequency range of the filter is from 10Hz to 50kHz NOTE The Crosstalk value depends very much of the frequency Since most Crosstalk is caused by capacitive or inductive coupling an average in crease of 6dB per octave and coupling element will result Units Since the Crosstalk result is a ratio of two levels relative value it can be expressed in units with no dimension only Following units may be chosen through the lt UNIT gt button Unit lin log Calculation 4 lin UActive filtered Uinactive lin UaActive filtered 100 Uinactive UActive filtere dBr log 20 log ctive fi te
23. measurements of level except noise are true RMS rectified Noise is measured as quasi peak value according to the CCIR 468 3 standard Both a 400Hz high pass and a 22Hz 22kHz band pass filter are available as a standard The two inputs of the A2 A2 D are DC isolated up to 300Vp and equipped with selectable input impedances to optimally match the output impedance of the device under test DUT As an option both inputs may also be Phantom powered The normalized input signals are available at the BNC connectors at the rear panel of the instrument A small built in loudspeaker allows acoustical monitoring of the measured signal The versatile generator of the A2 A2 D based on a Digital Signal Processor is capable of generating a large number of different test signals over the full level amp frequency range e Low distortion pure sine signal e Lowdistortion warbled sine e Dual tone IMD signal covering all standards e Symmetric square wave 50 50 duty cycle e Asymmetric square wave 40 60 duty cycle for phase reverse check e White noise e Pink noise The output impedance lt 15Q up to 600Q can be adjusted in a wide range as well in order to match the input impedance of the device to be tested As an option a RS 232 serial or IEEE 488 parallel interface may be installed into the instrument to remote control all A2 A2 D features from a PC Regardless of the type of interface AS04 a comprehensive Windows based software p
24. reciprocal value can be found by simply in verting the sign of the result e f expressed in a linear scale the reciprocal value can be calculated by building the reciprocal However expressing the SINAD in is not common NOTE The SINAD value expressed in dB is the negative of the THD N value expressed in dB Example THD N 70dB gt SINAD 70dB THD N 0 03 gt SINAD 3333 Prey V3 1 om 51 104 User Manual A2 Audio Test amp Measurement System IMD Function IMD Intermodulation Distortion is another form of distortion measurement The device under test DUT is stimulated with a signal being composed of a low frequency and a high fre quency tone If the DUT produces non linear distortions new frequencies will be added to the stimulating signal These distortion products are measured and set into relation to the total output signal of the DUT consisting of the stimulus plus the distortion products The IMD value is a ratio expressed in dB or in Test kra Iper Hiter Cancduager Level log station proiz i z p Fig 20 IMD Measurement Principle H 2 The advantage of the IMD measurement function in comparison to THD N is that its dual tone stimulus comes much closer to reality than a single tone test signal Furthermore distortions can be measured up to higher frequencies since the required bandwidth is only Bandwidth f2 n fi where nis the order of the distor
25. recording medium e g a tape during the recording or reproduction proc ess e Wow describes the modulations within the frequency range of 0 5Hz 6Hz which is perceived as a fluctuation of the pitch e Flutter covers frequency modulation in the range of approx 6Hz 100Hz results in an increase of the roughness of the sound The W amp F function measures the Wow and Flutter of tape recorders and turntables either weighted or unweighted according to various international standards from either a 3 15kHz or 3kHz signal Though several standards exist they fall into two groups within these groups the standards are functionally identical One group consists of IEC 386 DIN 45 507 BS 4847 and CCIR 409 They measure with quasi peak rectifier WRF weighting filter Fig 23 W amp F Weighting Filter Standards The other group comprising of NAB and JIS C 5551 measures with a VU like response Both groups use the same weighting curve The IEC group normally measures from 3 15kHz and the NAB group from 3kHz However in the A2 A2 D measurements may be made according to either standard and frequency there is no need to buy two different test tapes Pre Ty V3 1 om 63 104 User Manual A2 Audio Test amp Measurement System Standards ce All standards described before can be selected out of the W amp F menu that may be opened by a double click ot key lt W am
26. show a too long lt 2s time delay between their in and outputs Obviously the in and outputs must not be loceted too far apart so that they can be wired up through cables to the A2 A2 D To perform an internal frequency sweep proceed as follows 1 Select the measurement function for the sweep all functions available except W amp F 2 Enter the display mode to GRAPH by pressing the lt GRAPH gt button 3 Activate the frequency sweep mode by double clicking to the lt SWEEP MODE gt button and selecting the entry Frequency Consequently the bottom line of the display will show the actual sweep mode Frequency LOG 4 Use the lt LEVEL gt wheel to adjust the required generator output level This setting will be displayed on top of the screen The level of the generator will not vary during the sweep 5 Set the limits for the frequency sweep by using the lt START VALUE gt and the lt STOP VALUE gt keys Next choose the resolution that meets your demands 6 Press lt DO SWEEP gt to start the sweep The status line at the bottom of the display will show Freq RUNNING while the sweep is performed and switch over to Freq complete as soon as the sweep is finished You may abort a running sweep at any time by pressing lt DO SWEEP STOP gt again The next push of the lt DO SWEEP gt button will re start an other sweep recording and replace the previous trace NOTE Each new sweep replaces the old one as long as the actual trace h
27. the generator will change its output frequency as soon as the analyzer has successfully executed a valid measurement while with a tape sweep the generator will let each frequency present for a fixed time regardless of the status of the analyzer To fully understand this approach pleas read the subsequent explanation The A2 A2 D has a builtin algorithm to ensure taht only stable signals are measured In practice several consecutive samples are recorded and tested for stability If these samples are not stable enough more samples are recorded until the stability criteria is met The required duration to get a stable measurement result strongly depends on the selected measurement function and the stability of the incoming signal Normally the required time for the data settling is rather short typically 200 500ms However this duration cannot be predicted exactly and is never constant Therefore in order to allow the recording of a sweep even under worst case conditions THD N measurement at very low frequencies a special sweep mode has been introduced in the A2 A2 D This mode is called Tape Sweep Actually a tape sweep consists of a stepwise rising generator frequency with fixed time in tervals between the steps The user defined sweep parameters as well as the analysis and post rocessing capabilities are identical with the normal frequency sweep mode Recording a Tape Sweep To record a tape sweep onto a tape simply connect the
28. this mode e To switch back to automatic ranging nomal mode enter the menu again and select Auto NOTE The input attenuators amplifiers of the analyzer remain fixed in their range as long as the Fixed range mode is active rre 24 104 on Eii V3 1 A2 Audio Test amp Measurement System User Manual Connection of a Balanced Output to the A2 A2 D The device under test DUT is connected between pin 2 IN and pin 3 IN of the XLR input connector The shield may be connected to pin 1 but do not ground the shield on both ends of the connection in order to avoid ground loops DUT ATTENTION Input A2 Shielded cable Balanced output Fig 5 Balanced Connection to the A2 A2 D Connection of an Unbalanced Output to the A2 A2 D The device under test DUT is connected between pin 2 Signal and pin 3 GND of the XLR input connector ATTENTION Shielded cable wee eee Be sure not to have internal connection Fig 6 Unbalanced Connection to the A2 A2 D NOTE Never connect pin 1 and pin 3 together as long as you are not absolutely sure that the GND output of the DUT is galvanically isolated from earth If in doubt leave pin 1 of the A2 A2 D unconnected to avoid earth loops aca eae ae V3 1 om 25 104 User Manual A2 Audio Test amp Measurement System Monitor Outputs There are three BNC connectors and one headphone jack in the MO
29. unitin meas urement function Level only Therefore in order to change the generator unit it is necessary to enter the Level measurement function and to select the required unit Filters The A2 A2 D has two frequently used filters built in as a standard The 400Hz highpass and the 22Hz 22kHz Audio bandpass filter Both filters are built by a 3rd order stage with an edge steepness of 60 dB decade To activate one or both of these filters at a ime press the 400Hz or the 22 22k key re spectively Eee FR win Wot Janne Loser UNI e eo O gi oom 2 Although the definition of dBm is a power and not a voltage it is mostly handled as a voltage equal to the dBu representing the power into a 600Q load tae oe V3 1 om 45 104 User Manual A2 Audio Test amp Measurement System Furthermore the A2 A2 D is prepared to handle one or two additional weighting filters per channel for Level measurements Following filter options are available e A weighting filter order code AO4 e User definable filter order code AO5 e C message filter order code AO13 e 80kHz lowpass filter order code AO14 To activate the additionally installed filter s i e to insert it into the signal path press the lt WTD UWTD gt button If a filter is installed the LED behind the WTD will light up indicating that filter 1 is active If a second filter is installed on the same channel the next keypress to the lt WTD UWTD gt
30. very high Crest factor i e a high Vp Vams level ratio Therefore it is typical for Pink Noise that its amplitude measured Quasi Peak or RMS is never stable Warbled Sine The Warble signal is a sinusoidal signal with oscillating frequency The active generator fre quency defines the center frequency while the modulating signal has a triangular shape with 4Hz The Warble signal is best described in the frequency range showing a fixed amplitude that oscillates with about 4Hz and a 3 octave bandwidth around the center frequency set with the lt FREQUENCY gt softwheel Frequency The generator output frequency is set through the lt FREQUENCY gt softwheel This wheel has no end stops Turning it counter clockwise reduces the frequency or clockwise to in crease the frequency The limits of 10Hz and 100kKHzcannot be exceeded NOTE In some measurement functions the frequency range is reduced to a smaller bandwidth Refer to the corresponding measurement function to see the exact limits e gt lt gt gt The frequency is not controlled in a continuous fashion like with an analog generator controlled by a potentiometer but in discrete steps Pushing the wheel exchanges the step size between coarse and fine lt gt The selected step size is indicated by an active LED behind the respective sign e A slow i e stepwise turn of the softwheel change the output frequency by 1 6 octave steps in the
31. wheel once Each further push will toggle between the ZOOM and SCROLL mode To set the SCALE function back to AUTO mode push the lt SCALE gt wheel twice quickly The selected mode is always indicated by a LED behind the label Every change of the scaling mode AUTO ZOOM or SCROLL re draws the recorded traces completely in the new scale without loosing any information ZOOM The ZOOM mode allows to enlarge reduce the scaling units per division of the Y axis by turning the lt SCALE gt sofwheel in clockwise CW counter clockwise CCW direction Prey V3 1 om 39 104 User Manual A2 Audio Test amp Measurement System Zor SCALE e Every incremental step in CW direction of the lt SCALE gt wheel an increases the sensitivity of the Y scale i e A COW increment decreases the sensitivity i e enlarges the ATS displayed range of the Y axis tence The actual sensitivity is displayed on the left hand side of the graph Every zooming keeps the centre value of the Y axis at its place if possible In case that the 0 zero value would fall into the scale the range will be scrolled upwards so that the zero value corre sponds to the bottom line of the graph NOTE A fast turn of the lt SCALE gt wheel in the ZOOM mode reduces CW turn or expands CCW turn the Y scaling to the Min Max sensitivity SCROLL The SCROLL mode allows to scroll the range of the Y axis scale upwards downwards by turning the lt SCALE gt
32. A2 D Audio Test amp Service System and its components against defects in material or workmanship for a period of one year from the date of original purchase and agrees to repair or to replace any defective unit at no cost for either parts or labour during this period Restrictions This warranty does not cover damages that have resulted of accidents misuse lack of care the attachment or installation of any components that were not provided with the product loss of parts or connecting the instrument to any other power supply input signal voltage or connector type than specified In particular no responsibility is granted for special incidental or consequential damages This warranty becomes void if servicing or repairs of the product are performed by any other party than an authorized service center No other warranty written or oral is authorized by NTI Except as otherwise stated in this warranty NTI makes no representation or warranty of any kind expressed or implied in law or in fact including without limitation merchasing or fitting for any particular purpose and assumes no liability either in tort strict liability contract or warranty for products Note In case of malfunction take or ship prepaid your NTI A2 A2 D Audio Test amp Service System packed in the original packing to your nearest authorized service center Be sure to include a copy of your sales invoice as proof of purchase date Transit damages are not
33. B onena 63 lt A eea V3 1 HTE 101 104 User Manual K lt ADDITIONAL gt lt CROSSTALK gt lt DO SWEEPS lt FREQUENCY gt lt GEN SIGNAL gt lt GRAPH gt lt IMD gt lt IMPEDANCES ccceeeeeeeeeeeeeees 22 23 lt INT EXT gt 50 60 62 71 lt L REL gt i 47 lt L SEL gt 61 44 LME JERS ernie 32 34 35 lt MUTE gt 1 33 57 55 66 43 82 70 80 fas 15 we 42 lt SET REF gt 85 90 lt START VALUE gt 69 73 lt STOP VALUE gt 69 73 OOP Sae ar e a tessa 70 lt SWEEP MODE gt 69 71 73 lt THD N gt 49 lt UNIT gt 2 35 lt UNIT gt 45 48 lt W amp F gt 64 lt WTD UWTD gt 46 L Lasejjetisen raa aia Level Display Menu Measurement Ratio of IMD Signal Relative Measurement Selective Loudspeaker Internal M Main Input Channel Monitor Output Mains Power Manual Range Setting Scaling of Bar graph Scaling of Sweep Graph Measurement CROSSTALK 102 104 A2 Audio Test amp Measurement System Result Display SINAD THD N Memory for Instrument Setup for Sweep Curves Menu 3rd Level Unit Gen Status Line Graphics IMD Default Impedance Level Display Operation Overview Printer Type Ranging Resolution Meter Display Mode cece 34 Monitor Loudspeaker Outpu
34. E If working with a balanced load it is recommended to operate the unit in the FLOATING mode Unbalanced Operation When driving an unbalanced device it is recommended to connect pin 2 signal of the out put stage to the hot input connector of the DUT and to link pin 3 signal of the output stage with the ground of the DUT In this case operate the A2 A2 D in the FLOATINGmode By this way only the loss of half of the output level can beavoided On the other hand unbalanced loads may also be connected between pin 2 or pin 3 and pin 1 of the A2 A2 D output stage half side connection In this mode it is recommended to set the switch on the rear panel to GND in order to get an invariant reference potential Optional Transformer Output Stage Some applications require a complete galvanic separation between the generator output connectors and the device under test For this purpose a transformer option is available ar ticle code AO7 that adds a high quality Audio transformer behind the power amplifier of the A2 A2 D Pc Ty 28 104 on V3 1 A2 Audio Test amp Measurement System User Manual The A2 A2 D generator specifications as well as the output impedance circuitry are the same with and without the transformer option Please refer to chapter 8 Instrument Setup for further details Output Settings The METER display mode provides the best overview on the generator settings and meas urement results Therefore
35. NITOR section on the rear panel providing monitor signals for further processing Output impedance through the headphone connector is 68Q while the BNC connectors have an impedance of 600 The two connectors MAIN CHANNEL and ALT CHANNEL offer the signals of each input channel right behind the input amplifi oe m lt ers The level of these signals are always around 1V OdBV The third BNC output offers the READING signal which is the analogue signal of the MAIN channel after all the filtering and weighting but before its rectification see Input Block Diagram Please notice that the signal provided at the READ NG output is not necessarily the same as at the two other connectors Depending on the actual measurement function the charac ter of the READING signal will be totally different from the two other outputs e g with meas urement function THD N or IMD More detailed information about this topic are given in the respective chapters describing the measurement functions NOTE The MONITOR outputs are not calibrated and shall not be used for measurements Monitor Loudspeaker The READING signal is also fed to the internal loudspeaker The volume can be changed through the potentiometer on the front panel marked with the loudspeaker sign Overview e The input impedances may be selected through the lt IMPEDANCE gt key e The unit may be operated in the balanced or unbalanced mode by setting the lt FLOAT GND gt swi
36. OTE While a menu is open any other keypress than to the lt SCALE gt wheel will close the menu and execute the new command Generator Settings The generator output frequency amp level can be selected by the two softwheels labeled with lt FREQUENCY gt and lt LEVEL gt pha FREGUENCY i LEVEL Neither frequency nor level can be changed a gt TDA continuously as with a poti controlled analog pa generator but in discrete steps only By pushing the softwheel once the stepwidth N toggles between fine lt gt and coarse mode The actual selection is indicated by a lit LED behind the corresponding sign By turning the lt FREQUENCY gt or lt LEVEL gt wheels slowly or quickly the width of the step up down to the next value may be small or large as listed in Table 1 lt FREQUENCY gt lt LEVEL gt Coarse mode quick turn 10Hz 20Hz 100Hz 1kHz i 20dB logarithmic units 10kHz 40kHz 100kHz or factor 10 linearunits Coarse mode s ow turn 12 5 2dB 25 9 Fine mode quick turn 3 octave steps Fine mode slow turn 20 5 2dB factor 2 0 04dB 0 5 H H i Table 1 Softwheel Steps Furthermore the two generator outputs A and B can be muted by pressing the respective lt MUTE gt keys Otherwise i e if they are muted both outputs are permanently active The Display Modes With the three DISPLAY MODE keys the user may select one of t
37. SO3 for remote control of the analog functions of the A2 The included easyto earn Audio Measurement Programming Language AMSL allows to build up sequences and PASS FAIL tests for automated applications Demo disk available AO4 A weighting filter according to IEC 651 The filter may be activated with the lt WTD UWTD gt key For 2 chn measurements two filters are required AO5 User definable filter A pre wired board containing four operational amplifiers and the switching electronics but without passive components The user can build up a four pole active filter with freely setable frequency response For 2 chn measurements two filters are required AO7 Transformer output option Adds a transformer behind the electronically balanced output stage AO8 Phantom power option Installs either 15V or 48V phantom power to both input channels Replaces the low input impedance 200Q 1509 A010 Digital option PCB to upgrade an A2 instrument to an A2 D The option allows the generation and analysis of digital Audio signals according to AES and IEC958 standards Provides digital peak level RMS level THD N sampling frequency jitter status and bit statistics analysis Supports mixed signal applications AO11 IEEE 488 interface for A2 A2 D Allows remote control all functions of the instrument through a GPIB interface Cannot be installed together with RS232 A012 FFT option for A2 D Performs spectral analysis of the mai
38. Test amp Measurement System User Manual GRAPH Printouts Any graph may be printed out to a connected printer by pressing the lt PRINT gt button which is located on the ight hand side of the front panel Consequently the complete graph in cluding all curves the grid and the scaling will be printed To select the printer driver double click on the lt PRINT gt key and choose from the menu that will open Details about the printers and its selection are given in chapter 7 Printouts P 2 CHN Output Imp lt 150hm Filter Input Imp 100k0hm Sine Off A 0 09dBu 1 000kHz 0 00dBu 1 000kHz B 2 26dBu 1 000kHz D COB wenn meet aiming i e ae wt iy 20 00 Hz Frequency log Fig 16 Example of a Printed GRAPH Display The A2 A2 D is not blocked during the print out The print process is handled in the back ground so that any measurement may be performed or continued in the meantime Store amp Recall Graphs Sometimes when using the A2 A2 D no printer may be available for documentation There fore to allow later printouts of recorded graphs the A2 A2 D offers four memory locations to store and recall a complete graphs in each of them with all the curves and the scaling in cluded This memory is battery backed up to allow to disconnect the instrument from mains power and to return to the office for the printout The detailed description on how to store and recall graphs is described in chapter 6 Sweeps Prey V3 1
39. Thinkjet allow to send the respective commands to the printer P hP Deskjet Do FormFeed ivati i RESET Printer Activation of the EXIT entry or any keypress will close the EXIT menu without changes NOTE The RESET command meets the specific demands of the active printer driver i e will not be understood by the other inactive printer types rrt 82 104 om Eii V3 1 A2 Audio Test amp Measurement System User Manual Printer Settings Since there are a lot of possible settings for the different printers the following list shall give a quick guide for the DIP switch settings of those printers who have been tested to operate properly with the A2 A2 D EPSON FX 80 IBM Proprinter Parameter Settings Page length 8 Automatic form feed OFF inactive Automatic line feed OFF inactive Automatic CR OFF inactive Print Quality Selectable by user Graphics density 120dpi Text density 12cpi EPSON LQ 550 LQ 1050 LQ 550 LQ 1050 Function Set Function Character set USA ON Character set GER Character set USA OFF Character set GER Character set USA ON Character set GER Draft quality OFF Cursive Draft quality OFF Bi directional print Condensed printing OFF not used Graphics ON Single sheet Single sheet ON 6k Buffer 12 Page length ON 12 Page length Skip over perforation OFF Skip over perforation Switched off OFF Parallel interface Auto LF OFF Parallel interface 8k Buffer OFF Baudrate not used
40. User Manual A2 Audio Test amp Measurement System User Manua A2 Audio Test amp Measurement System Version 3 1E A2 firmware V2 0 or higher V3 1 July 01 Ben N A2Pro Manuals User ManualEnglish a2um_31e_nti doc Test amp Measurement System 2 104 EE V3 1 A2 Audio Test amp Measurement System User Manual CE DECLARATION OF CONFORMITY We the manufacturer NTIAG Im alten Riet 102 FL 9494 Schaan Principality of Liechtenstein Europe hereby declare that the product Product Name Audio Test amp Service System Model Number A2 Year of Construction 1995 conforms to the following standards or other normative documents EC Rules 89 392 91 368 93 44 93 68 73 23 89 336 92 31 Harmonized Standards IEC 65 IEC 68 2 31 IEC 348 EN50081 1 EN50082 1 EN50140 EN 61010 1 This declaration becomes void in case of any changes on the product without written authorization by NTI Date Schaan 28 02 1995 Signature D DAE Position of Signatory Product Manager Test Instruments Samples of this instrument have been tested and found to conform with the statutory protective requirements Instruments of this type thus meet all requirements to be given the CE mark FETI V3 1 om 3 104 User Manual A2 Audio Test amp Measurement System 4 104 E oge g bie i Eii V3 1 A2 Audio Test amp Measurement System User Manual INTERNATIONAL WARRANTY Limited Warranty NTI guarantees the A2
41. VEL L REL NOISE or N REL sweep without stimulating the DUT with a signal Since all these measurement func tions rectify the wideband signal the absence of a stimulus would result in no A2 A2 D input signal variation at all i e the measured result would be stable for all frequencies regardless of the charactristics e g fre quency response of the DUT Graphics Cursor When turning the lt FREQUENCY gt softwheel after having recorded a sweep curve a cross hair becomes visible in the graph at the generator frequency while the bottom line of the LCD will show the interpolated measurement value The cursor disappears as soon as the upper or lower end of the frequency axis is reached and it is brought back as soon as the generator frequency is in the displayed range again In case of a 2 channel measurement the cursor is assigned to the curve of the main chan nel which is drawn in black If you wish to measure the curve of the alternate channel simply press the lt A B gt key to toggle the active channel The graph is re drawn with inverted line style and the cursor is available on the other trace Keep in mind that the cursor is not printed out with the curve rre 74 104 on Eii V3 1 A2 Audio Test amp Measurement System User Manual Tape Sweep Tape sweeps are very similar to normal frequency sweeps except that the frequency steps last for a predefined duration In other terms with a normal frequency sweep
42. a from 3 s econds only up to one that takes almost a week to complete The scale of the Xaxis always starts at time zero The resolution of the sweep i e the number of samples to be recorded within the selected sweep duration T sec may be set through the Resolution menu that is hidden behind the lt RESOLUTIONS gt key Keep in mind that the time interval At sec equals T sec At sec _ _ _ NoOfSamples Equation 3 Time Sweep Interval Calculation and must not be shorter than the settling time that the A2 A2 D requires for a single measurement 300msec The sweep is started by pressing the lt DO SWEEP button The Time Sweep mode is the only one that allows to enter the GRAPH display mode in measurement function W amp F In all other sweep modes W amp F cannot be recorded Pro Ty 80 104 om Eii V3 1 A2 Audio Test amp Measurement System User Manual Table Sweep As an alternative to frequency sweeps defined by a start amp stop frequency a fixed output level and number of points the A2 A2 D also offers the possibility to execute Table Sweeps They are driven by a discrete number of freely defined generator frequencies amp levels at which the measurement function is recorded Such a set of frequency Level pairs is called sweeptable Obviously the output level of a table sweep may be constant while the set of frequencies must change The table sweep mode allows the user to tailo
43. ackage is included supporting all operation modes offering the possibility to store all results and allowing to write program sequences in the easytotearn Audio Measurement Sequence Language AMSL for fully automatic measurements Prey V3 1 oe 11 104 User Manual A2 Audio Test amp Measurement System How to use this Manual This User Manual has been written to serve as a complete reference document for using the A2 A2 D as a solution for your measurement requirements Maintenance procedures such as installation of the instrument are placed at the beginning while not so frequently required tasks such as re calibration are filed at the end of the manual The best way to familiarize with the instrument is to place the A2 A2 D in front of you and to read through the chapters 2 Installation and 3 Getting Started This way it won t take long to feel atease with the instrument and its many features Do not operate the instrument without reading through the chapter 2 Installation Important information about mains voltage selection and fuse rating is given therein rre 12 104 on Eii V3 1 A2 Audio Test amp Measurement System User Manual 2 INSTALLATION Unpacking Your new A2 A2 D comes along together with some accessories Please check whether all of the following items are enclosed e A2 A2D Audio Test amp Service System e Mains power cable e Spare fuse for 110VAC e A pair of rack mount wings e This U
44. as not been kept see chapter Keep a Recorded Trace Y Axis Units and Scaling The lt UNIT gt button allows to set the unit of the Y axis measurement function Please no tice hat the graph with all recorded traces will be re calculated and re drawn upon a change of the unit To change the scaling of the Yaxis use the lt SCALE gt wheel as described in chapter GRAPH Display Mode p 38 Re Scaling of the Frequency Axis If a sweep has already been recorded but the displayed frequency range is too large it can be adjusted easily by re setting the Start and Stop frequency Set the generator frequency to the desired value of the lower upper border of the frequency range Next press the lt START VALUE gt lt STOP VALUE gt button respectively Conse quently the recorded graph will be re drawn in the new range NOTE The recorded graph is not measured again but re drawn in the new range only The parts of the curve s outside the displayed graph are not lost but just not visible It is therefore always possible to return to the original frequency range te oe V3 1 om 73 104 User Manual A2 Audio Test amp Measurement System Frequency Sweeps in Different Measurement Modes The A2 A2 D2 can perform frequency sweeps in the measurement functions Level Level Relative Level Selective THD N IMD Noise Noise Relative Crosstalk and Phase but not Wow amp Flutter NOTE It is useless to perform a LE
45. axis by using the lt LEVEL gt softwheel Again the nu merical values that correspond to the position of the cursor are displayed in inverse let ters on the bottom line of the graph The cursor will disappear as soon as the upper or lower end of the X axis is reached and re appears as soon as the generator frequency evel returns into the recorde range of the sweep X axis To take full advantage of the Cursor feature please notice the following e The lt FREQUENCY gt lt EVEL gt softwheel may be operated in either fine lt gt or coarse mode e If the cursor is placed between two actually recorded measurements the displayed val ues will be interpolated linearly e It is possible to enter the METER display and return to the GRAPH display at any time also during a running sweep without loosing any information e The cursor will not beprinted out together with the graph e In the Time sweep mode there is no cursor function available Y Scaling The lt SCALE gt softwheel gives you the possibility to adjust the scaling of the Y axis in the GRAPH mode according to your needs e In the AUTO mode the A2 A2 D calculates the optimum scaling out of the valid meas urements from all the traces within the graph e The ZOOM mode allows to manually adjust the sensitivity of the graph e The SCROLL mode allows to scroll the displayed graph through the avilable range To leave the AUTO mode push the lt SCALE gt
46. ay be set through the lt FREQUENCYs gt softwheel Fig 9 IMD Testsignal The level ratio between the low and the high frequency component is either 1 1 4 1 or 10 1 refer to chapter 5 Measurement Functions Consequenty there are six different IMD test signals available according to the SMPTE and DIN standards To define one of them as default signal the MD Default menu must be opened by a double click on the lt IMD gt key In normal operation the IMD TestSig will be activated automatically as soon as the IMD measurement function has been entered Alternatively it may also be activated manually through the Alt Signal menu wT 30 104 Eii Eii V3 1 A2 Audio Test amp Measurement System User Manual Noise The generator of the A2 A2 D offers White and Pink Noise both with a bandwidth being lim ited to 20kHz in order to maximize the energy falling into the Audio band e The characteristic of White Noise is a constant energy density for all frequency bands with identical width e g width 100Hz Consequently the noise spectrum will show a constant amplitude energy if analyzed vs the linear frequency axis or a linear rise of 10dB decade if plotted vs the logarithmic frequency axis e On the other hand the amplitude of Pink Noise shows a linear decay of 10dB decade if analyzed vs the linear frequency axis or a constant amplitude if plotted vs the logarith mic frequency axis NOTE Pink Noise has a
47. ayed IMD value is calculated according to _ Sidebands Signal f 2 Sidebands The maximum IMD result is limited internally by the A2 A2 D to 10 which equals 20dB Higher values would overload the reference circuitry Since the Crest factor of the IMD signal is higher than the one of a pure sine signal the maximum output level has to be limited too in order to ensure that the output amplifier does not clip at the maximum peak amplitude Obviously the maximum IMD amplitude depends on the selected standard 1 1 1 4 or 1 10 see next chapter Standards Both the frequency of the lower tone f7 and the level ratio of the two tones are standardized Since several standards exist the A2 A2 D was designed to allow IMD measurements ac cording to all these standards The list of the implemented standards is given below DIN 45403 4 Frequency f2 shall be either 4kHz or 5kHz The amplitude ratio shall be preferably 4 1 but 10 1 is also allowed IEC 268 3 The frequency f2 shall be 8 f1 f1 shall be preferably 250Hz Amplitude ratio is 4 1 SMPTE Low frequency shall be 60Hz High frequency either 7kHz or 8kHz Ampli tude ratio 4 1 Some standards fix the high frequency to 7kHz or 8kHz However it may be useful to vary the high frequency over the entire frequency range Therefore the A2 A2 D allows to set the high frequency freely in the range from 4kHz to 40kHz TUEN To select one of the available standards enter the IMD Defau
48. behind the power amplifier of the A2 A2 D This features mainly allows an additional galvanic separation of the generator output and a perfect balancing of the outputs Torisme soe te Peover tay er The generator specifications remain the same with and without the transformer and also the impedance circuitry remains active Phantom Power AO8 The A2 A2 D can be equipped with Phantom power on both inputs Installing phantom power replaces the lowest input impedance of 2009 1509 The Phantom power option allows to select either 15V or 48V as supply voltage level in the installation process It is fixed and can be changed by soldering only NOTE As soon as the Phantom power option is installed the lowest input impedance is no more available Accessories Overview Code Article AA10 Soft carrying bag for A1 A2 or A2 D Perfectly protects the instrument on all sides Allows the instrument to be operated in the bag even in vertical position Comes complete with shoulder strap AA12 Additional User Manual this document AA21 A2 A2 D Service Manual Contains all schematic diagram assembly drawings and the complete calibration procedure AA22 Modem Cable Allows the remote control of an A2 A2 D instrument from a PC through a modem link under AS04 software Requires installation of the RS232 interface 3382 14 Measuring Microphone 3384 2 Measuring Microphone rrr tT V3 1
49. cade 24 dB octave at any frequency e Fixed bandpass filter with 40dB decade steepness at any frequency e Any characteristics consisting of up to four kink points In case of questions about the filter design or realization contact your local NTI agency Switch Control User Filter board AO5 ORORO 0000 0000 OoO e OOK Filter Input gt GOO Analog GND lt gt ORORO 15V DC gt 15V DC gt Filter Output lt Digital GND lt gt Fig 27 User Filter Layout 92 104 V3 1 A2 Audio Test amp Measurement System User Manual User Manual A2 Audio Test amp Measurement System C Message Filter AO13 80kHz Lowpass Filter AO14 Frequency Hz Gain dBV Limits aBV 60 55 7 2 1300 0 7 1 100 42 5 2 1500 1 2 1 200 25 1 2 1800 1 3 1 300 16 3 2 2000 1 1 1 400 11 2 1 2500 1 1 1 500 7 7 1 2800 2 0 1 2 600 5 0 1 3000 3 0 1 3 700 2 8 1 3300 5 1 2 y 800 1 3 1 3500 7 1 2 900 0 3 1 4000 14 6 3 1000 0 0 reference 4500 22 3 3 1200 0 4 1 5000 28 7 3 100 ik 10k 100k Prequency iz Fig 29 80kHz Lowpass Filter Characteristics Level dBU Frequency Hz Fig 28 C Message Filter Characteristics Pip peep rre V3 1 om 93 104 94 104 HTI V3 1 A2 Audio Test amp Measurement System User Manual Transformer Option AO7 The transformer option adds a high quality Audio transformer
50. chine into the recording mode The 1kHz output tone of the A2 A2 D shall be recorded for at least 3 seconds 5 Press the lt DO SWEEP button to start the tape frequency sweep By this the message Tape RUNNINGwill be displayed on the bottom line of the LCD 6 As soon as the sweep is completed Tape COMPLETED will appear on the bottom line indicating that the tape recorder may be stopped followed by the message Tape x x Sec Step NOTE When using a 2 head tape machine the output of the replay head may be connected to the analyzer of the A2 A2 D in order to directly measure the response of the DUT However keep in mind that certain tape machines those with one head only provide an output signal that monitors to the preamplifier out put but not the recorded signal 7 Rewind the tape to the starting point and use the recorded track as the source for an ex ternal frequency sweep A lag f fet LH point tocondlitlon with falling frequency Ditforant teequency from 7 kHz Is ster condition Ik popu p pul Swaas d ron 5 E Time 5 Fig 24 Tape Sweep rre 76 104 om Eii V3 1 A2 Audio Test amp Measurement System User Manual External Sweep The A2 A2 D is capable of performing external sweeps i e to synchronize itself to the output signal of an exte rnal device such as a tape recorder or a CD player Obviously the charac teristics of such an external signal
51. coarse mode or 0 5 steps in the fine mode e A fast turn in the coarse mode changes generator frequency to 20Hz 100Hz 1kHz 10kHz 40kHz 100kHz while in the fine mode each fast turn causes the generator to jump in3 octave steps Level The generator level is controlled through the lt LEVEL gt softwheel Pre Ty V3 1 om 31 104 User Manual A2 Audio Test amp Measurement System a Like the output frequency also the generator level is controlled in dis crete steps of 2dB coarse or 0 05dB fine Please notice that the absolute limits of 30dBu 27 7dBV 24 49V and 97 7dBu 100dBV 10uV cannot be exceeded e A fast turn of the lt LEVEL gt wheel in the coarse mode causes the generator to jump by 20dB to even values dBu or dBV selected or to the next decade V selected e A fast turn in the fine mode forces the generator to jump jump by 2dB to even values or with an increment of 1 V Readback In case that the input impedance of the device under test is relatively low a major output voltage drop on the A2 A2 D may occur Actually the output voltage Uo may be calculated according to following formula Obviously it may happen that the generator voltage Ug set by the lt LEVEL gt wheel differs from the actual output voltage U o at XLR connectors In order to detect such cases the A2 A2 D is equipped with the Readback function that measures the true voltage Uo between pin 2 and pi
52. ct the external source to the input of the A2 A2 D through the Device Under Test 7 Check for the right settings of the external generator and let it start the sweep 8 If the external sweep starts with a 315 or 1kHz header the A2 A2 D will display Freq STARTING to indicate that it is waiting for the sweep to start The starting condition itself is an abrupt change from the 315 Hz or 1kHz header tone to alower frequency 9 In case of a missing header the sweep can be started manually by pressing the lt DO SWEEP gt button 10 Every abrupt decrease of the frequency during the sweep recording is interpreted as STOP command see Fig 24 NOTE Every analog audio analyzer requires a certain time to settle on the in coming frequency For this reason only stepped frequency sweeps may be processed Preferably use theTape Sweep of the A2 A2 D to get best results Nevertheless if the increase of frequency is not too fast even continuos sweeps may be handled correctly tae ae V3 1 om 77 104 User Manual A2 Audio Test amp Measurement System List of Reference CD Tracks Stepped Sweeps e Test CD Hessischer Rundfunk Track 18 35 8s step LEVEL THD N e PHILIPS Audio Signals disc 1 Track 8 23 8Hz 20kHz 60s step w o 1kHz header Gliding Sweeps e DENON Audio Technical CD Track 36 20HzZ20kHz in 50s LEVEL e Test CD Hessischer Rundfunk Track 36 20Hz 20kHz in 50s LEVEL e PHILIPS Audio Signals disc 1 Track 5
53. d to replay head is an ex act multiple of the time period duration of one cycle of the wow fre quency The effect is that of a comb filter For the same reason to get a more reliable result rewind and repeat the measurements several times and average the results Only one recording is necessary W amp F Signal Analysis By pressing the lt SCOPE gt button the waveform of the demodulated wow amp flutter signal will be displayed on the screen Regular periodic wow amp flutter can be identified from this wave form From the frequency the offending rotating components can be deduced capstan pinch wheel idlers intermediate wheels etc TETI V3 1 om 65 104 User Manual A2 Audio Test amp Measurement System Phase Function This function evaluates the interchannel phase in degrees i e it measures the phase shift of the active channel against the inactive channel reference channel The phase correlation of the two channels is displayed in the full range of 180 degrees To enter the Phase measurement function press the lt PHASE gt button The LCD will show PHASE and the measurement result IEVEI HN NUkiF CGR TALC HATE a cs a Inc _ es a A positive measurement result e g 30 with channel A being active means that the signal of channel A passed the zero volts line 30 before the signal of channel B did Adillaminaled T
54. e of a faster settling It is therefore recommended for all measurements where the generator acts as the signal source and where the DUT shows no frequency shifts The second method i e synchronizing the bandpass filter to the input frequency is best fit ted for all measurements where the stimulus of the DUT comes from an external generator e g measurements from a tape or a remote A2 A2 D or To set the control of the center fre AT quency to either mode use the lt INT C EXT gt button Each press toggles be tween the two settings e INT means that the frequency is locked to the generator frequency e EXT will lock the center frequency PUB of the bandpass filter to the domi oa nant input frequency Hint The status of the lt INT EXT gt key only has an effect for measurement functions with variable filters such as THD N L SEL and X TALK BART VALLE Units Since Level Selective is an absolute measurement the available units are the same as for the measurement function Level V dBV dBu dBm Applications e Spectral analysis of stationary signals e Accurate level measurements below the wide band noise floor e Accurate frequency analysis in a noisy environment rre 62 104 on Eii V3 1 A2 Audio Test amp Measurement System User Manual Wow amp Flutter Function Wow and Flutter W amp F describes the frequency modulation that is introduced by an irregu lar motion of the
55. ection Output Stage BNC Connectors CDs with Reference Tracks CE Declaration of Conformity 0 0 3 Centronics Connector Fin Assignment 00 004 87 Interface Channel Balance 48 Clock internal 3 Coarse Mode n se Connection Balanced Unbalanced Contrast Crest Factor of IMD Signal ninicsncinucstiniceancnissninnaicetnicna 53 of Pink Noise Crosshair Crosstalk CUSO ioi Bandwidth of IMD Measurement cceceeeeeeeeee 52 of Noise Signal DIN of Sine Output Signal 31 45403 4 Bar graph 45507 Baudrate Menu Standard for IMD Beam Finder Display Block Diagram BACHE io3 ccsess heneainexucacshuneaneecvraaneapasunces 21 GOntrASD case ccenesssscetelsiieligee vance ees edavedes 21 pippe 100 104 Eii Eii V3 1 A2 Audio Test amp Measurement System GRAPH Mode 0 ceeeeee aes OB METER Mode 34 Mode Overview 34 of Measurement Results Overview cee SCOPE Mode Screen Saver Distortion Drift W amp F Duty Cy Cle issii aoina 30 E REN scasivecesed siesta attidensaaizai aniccxinanndensseaneeeat 14 Environmental Conditions 0 13 EPSON Printer enrian 83 External Notch Filter Synchronization 0008 50 Sweep Control 0 Sweep Synchronization Synchronization of Narrow BP Filter 60 62 F Fab Requirement cesses 13 F
56. ed input wiring and the connector pin assignment of one channel The circuit is a true instrument grade differential input Both input pins 2 and 3 are loaded with 100kOhm to ground Additionally the input impedances are applied between the two pins The inputs are fed to the microprocessor controlled input attenuator amplifier that adjusts the level of the input signal in order to achieve a high dynamic range at very a very low distortion Input Output Impedance Selection In addition to the input impedance selection a menu is available to choose all available con figurations of the input and output impedances To enter this menu double click on the lt IMPEDANCEs key wisehaNoR The mped menu allows either to couple the input to the output impedance or to let the operator fix one impedance while having the other one switchable To select your preference move the m arrow with the lt SCALE gt wheel and confirm your selection by Imped pushing the lt SCALE gt wheel once Always leave the menu Inp 200 through the EXIT entry gt pee soe Optionally the input connectors of the A2 A2 D can be equipped with a 15VDC or 48VDC Phantom power to directly connect a Out 200 capacitor type microphone Please notice that the Phantom Out 600 power option replaces the LOW input impedance Please refer to Rout Rin chapter Phantom Power A08 for more details Depending on the configuration the displayed input impedance Rin
57. eee 81 Tape Head 65 Sweep 75 Technical Specifications THD N Measurement Time Sweep Transformer Output Option True RMS Detector U Unbalanced Connection Operation Unit dBm 45 dBu 44 dBV 44 Degree 66 Generator Level 36 of Sweep Graph 38 Selection osi asn eeaeee 35 A2 Audio Test amp Measurement System ETa D Seevecd ines eeeecasteviavaseeed 51 THD N 51 A E tate dues 44 Uploading of Sweep Data 81 User Interface adinei 18 W amp F Drift Measurement Function Menu Record amp Replay Replay Only Signal Analysis Standards A Test Signal Warbled Sine 6 31 Warbled Sine Warranty Weighting Filters White Noise Level Selective Analysis 61 Output Signal nos siccesrcsncsencprreereverderniemaericen Worldwide Support Wow amp Flutter X X Axis of Amplitude Sweep of Frequency Sweep XLR Pin Assignment 00 0 ee X Scale of Sweep Graph 0 ee 40 KTA Kleiser See Crosstalk Y Y Axis of Amplitude Sweep of Frequency Sweep Z Zoom Bar graph Sweep Graph BETI 104 104 bie ii Eii V3 1
58. ehind the respective label Pc Ty 36 104 V3 1 A2 Audio Test amp Measurement System User Manual Input Display On the bottom end of the METER display additional information about the input signals are available The displayed values show the input voltage and frequency measured right be hind the input connectors If the 2 channel Level function is used frequency and level of both input channels are shown while the parameters of the active channel together with the input impedance of the analyzer are shown with all single channel functions This Input display is very helpful for all non Level measurement functions e g THD N IMD Noise etc that do not display the input signal level For instance in the IMD measurement mode it is important to know the frequency and level of the input signal to allow the proper interpretation of the IMD results Therefore this information is shown on the Input display In case that the incoming signal is too small or too noisy to be measured no frequency level values are displayed NOTE The input level results are always RMS values regardless of the selected measurement function The measuring bandwidth is 500kHz without any weighting filter being involved Printouts The METER Display display can be printed out to a printer by pressing the lt PRINT gt button The printout contains all relevant information to document the measurement result Output Imp lt 150hm Inp
59. eighting mode on top along with the generator input level and frequency If a signal consisting of random noise is applied to the A2 A2 D the frequency reading will not be stable since no periodic signal is found Units The available units in function Noise are dBq and Vq where the q stands for Quasi peak rectified The reference voltage OdBq for the Quasipeak rectifier is 0 775V Filters Noise measurements can be done either weighted or unweighted whereof in both modes a specific weighting filter is active This is necessary according to the standards since unlim ited bandwidth would lead to an unlimited high noise signal e Press the lt WTD UWTD gt key to enter the weighted mode where the CCIR 468 3 filter is active LED WTD lights up e f the unweighted mode is selected the 22Hz 22kHz Audio Bandpass is activated automatically LEDs UWTD and 22 22k are lit tae ae V3 1 oe 55 104 User Manual A2 Audio Test amp Measurement System Noise filters 183120 a Frequency tiz Frequency sweep Fig 21 Noise Weighting Characteristics Applications Noise measurements are helpful if the noise content of the signal is dominant e g to measure the minimum output level of an amplifier Please notice that it is essential to termi nate the inputs of the DUT properly in order to avoid the introduction of external noise NOTE Do not use the Noise function to evalua
60. ents the absolute input voltage measured against the OV ref erence potential GND On the other hand the dBx units express the input voltage in a logarithmic scale vs different reference voltages Each of these units can be converted into any other by one of the mathematical equations listed in Table 2 l RMS Root Mean Square This is the energy equivalent value of the signal rreo 44 104 on Eii V3 1 A2 Audio Test amp Measurement System User Manual Unit lin log Reference Calculation V i ISO unit dBV 1 000V 20 1og ULV 1 000V dBu 0 7746V 20 log u v 0 7746V dBm imW 20 log u Vv JimWw R42 Table 2 Level Unit Conversions NOTE The unit dBm in the LEVEL functions is handled as the dBu unit as suming a load impedance of 6009 To alter the selected unit simply press the lt UNIT gt button Each press changes to the next unit available in that function To toggle between the dBm and the dBu unit open the 3rd Level Unitmenu behind the lt UNIT gt button by double clicking to it in the measurement function Level 3rd Level Units Select the unit of your convenience with the lt SCALE gt wheel and confirm by pushing to it The menu closes automatically gt Unit dBu after the selection Leave it through the EXIT entry or by ee pressing any key in case that no change is required Please notice that the generator level unit is coupled to the level measurement
61. ep Graph Serial Interface Option Number of Instrument Set Reference Voltag ccceeee 47 Settings of Generator of Printer of Sweep Setup of Instrument 85 Signal to NOiSe c cece eee SINAD 0 cescccstaacescecssteiisttes ence dcsaetenciee SMPTE IMD Measurement ccceeeeeeeeeeeees 53 Standard for IMD Softwheel lt FREQUENCY3 gt lt LEVEL gt 16 39 lt SCALE gt Operation Speaker internal Specifications Speed Error Square Signal Standard Stereo Level Measurement Separati Stop ValUCreissccinndn cantare 69 Store amp Recall Instrument Setup 85 Sweep Graph Sweep Amplitude Mode RS232 Availability of Modes Connector Cable ccccccccsesseseesesee eee 87 CUISOM e seecseesseeeseeeseeceeteeeeeesctees External Control ccceesseeeesreeeeeeeeees v3 1 HTE 103 104 User Manual Frequency Mode cccceesseseeeeeeeeeees 73 Limits of X Axis Mode Selection Number of Samples Overview Range of X Axis Recall Re Scaling Resolution Settings Store Synchronization Table Mode Tape Mode Time Mode Y AXIS 73 79 Sweepmode Menu ceeeeeeeeee eee 69 Symmetric ee See Balanced Synchronization of Filter of Narrow BP Filter of Notch Filter of Sweep T Table SWe cece eee eeee cneeeee
62. eplay W amp F Signal Analysis Phase Function Applications Filter Overview ce PD DITIONAL FUNCION secsscsicuvndsicecwner sass vcecsnteaiexnaccunnasvexnhanaiedlenaaurteadwnienasieenhdedaacicnvidd sunteiinuae Gs HOWE PS cfievecseencteceaeas ceceerdt ee AASA Preparing a Sweep Selecting the Sweep Mode Setting the Sweep Limits amp Resolution Performing a SWeeD ceeeeeeeee Synchronization Internal External Sweep Recording Keep a Recorded Trace Store amp Recall Sweeps Sweep Modes Frequency Sweep Y Axis Units and Scaling Re Scaling of the Frequency Axis Frequency Sweeps in Different Measurement Modes Graphics Cursor Tape Sweep 75 Recording a Tape Sweep External Sweep Preparing an External Sweep List of Reference CD Tracks Stepped Sweeps Gliding Sweeps Amplitude Sweep Units of X Y axis Time Sweep Table Sweep Sweep Data Upload to a PC 7 PRINTOUTS ceccescesseeeceeseeenecacecsecenecacesaesenesacesaeseaesasesaeseaesaeeseeseaesenetneeaseaes Printer Driver SEI CHOI eissira aietara aaae e aea Eria a Tara A aea aeiaai Printer Settings EPSON FX 80 IBM Proprinter EPSON LQ 550 LQ1050 hp Laserjet Deskjet 83 Printer EmO ernaar a eaa Eaa a aa aaa aaa a aAa EEE Er EET 83 8 INSTRUMENT SETUP secssessecistecsscecsvecesivescensieesienciveceeeeseeieneasieesieecetenerneeeny 85 Store amp
63. erface is a fully PC compatible serial interface using the female 9 way Sub D connector The A2 acts as the DCE unit and has therefore the lines already twisted so that the cable to connect to the PC is a straight connected through cable The baudrate is selectable in the setup menu Please refer to Baudrate Selection on page 90 for their settings Serial inter ace Pin No Name Type Description 1 5V Output 5V from A2 2 TXD Output Send DATA 3 RXD Input Receive DATA 4 DTR Input Data terminal ready 5 RSGND I O DATA GND 6 DSR Output Data set ready 5V 7 CTS Input Clear To Send 8 RTS Output Request To Send 9 NC V3 1 87 104 User Manual A2 Audio Test amp Measurement System Cable To connect the A2 A2 D serial interface with the PC a standard 1 1 cable is required which can be purchased easily When assembling the cable yourself please follow the wiring shown below SJBD ras SU3 D female Fig 25 MD9 Male to MD9 Female 88 104 V3 1 A2 Audio Test amp Measurement System User Manual 9 OPTIONS amp ACCESSORIES The following tables list all available options and accessories of the A2 A2D with a brief description of their characteristics and performance Please notice that all options must be installed by NTI or an authorized representative to maintain the warranty Options Overview Code Article AO1 RS232 interface with MS DOS based software package A
64. evel Relative Units The Noise Relative function offers several units which can be chosen through the lt UNIT gt button lin log Calculation lin Uin UREF lin UIN UREF UIN 20 log EF 100 Filters Like Noise measurements Noise Relative can be measured as well either weighted or unweighted see p 55 e Press the lt WTD UWTD gt key to enter the weighted mode where the CCIR 468 3 filter is active LED WTD lights up e f the unweighted mode is selected the 22Hz 22kHz Audio Bandpass is activated automatically LEDs UWTD and 22 22k are lit pippe V3 1 om 57 104 User Manual A2 Audio Test amp Measurement System NOTE In the Noise Relative measurement function the weighting by a CCIR 468 filter applies to both the input and reference signal Therefore the gain with and without the filter is equal at 1kHz only 58 104 pippe Ln is i V3 1 A2 Audio Test amp Measurement System User Manual Crosstalk Function The Crosstalk function also called Stereo Separation measures the interaction from one channel to the other The measurement is done by sending a sine signal through the one channel while the selective output level of the other channel the one that is not stimulated is measured at a certain frequency The resulting level ratio between the muted channel and the active channel is the Crosstalk value Like with the Level Relative function the Crosstalk
65. generator range Sweep Resolution 3 200 points External Sweeps automatically synchronized Analog Analyzer Number of Channels 2 simultaneously operating inputs balanced fully differential roc Tt 96 104 om V3 1 A2 Audio Test amp Measurement System User Manual Impedance Input voltage Phantom Power CMRR Digital Analyzer Input Format Impedance Sampling Frequency Locking Range Measuring Accuracy Jitter Function Input Level Level Function Range Residual Noise Flatness Rectifier Type 3dB Bandwidth 100kQ 50pF 600Q 200 Q 1509 selectable max 300V peak 200Vrms optional 15V or 48V replaces 200Q 1502 impedance gt 80dB 20Hz 20kHz Professional according AES 3 and Consumer according IEC 958 optical TOS link 1100 750 32kHz 44 1kHz 48kHz hous eclock or input clock 25 52kHz 2ppm 0 1 40ns continuously measured 0 1 10Vpp 1pV 200V 120dBV to 46dBV lt 1 5uV short circuit 22Hz 22kHz 0 05dB 20Hz 40kHz 0 1dB full band true RMS gt 250kHz Total Harmonic Distortion THD N Fundamental Range Display Range Input Voltage Residual THD N Input gt OdBV 3dB Bandwidth Rectifier Type Phase Frequency Level Range Level Difference Accuracy IMD Standards Frequency Ratio Low Frequency High Frequency 10Hz 50kHz 0 001 100 100dB to 0dB 5mV 200V lt 95dB typ DIN audio BP lt 92dB 0 0025 or 10uV DIN audio bandpass 2Hz 250kH
66. he lt UNIT gt button has no effect in the PHASE function due to the fact that degrees is the only available unit NOTE The max allowed level difference between the input channels is 18dB Applications e Phase response of the device under test output to input e Phase relation of the two output channels e Tape head azimuth adjustments Pro Ty 66 104 om Eii V3 1 A2 Audio Test amp Measurement System User Manual Filter Overview The table below list all standard and optional filters of the A2 A2 D and indicates their availability for the different measurement functions Y available compulsory Meas 400Hz 22 22k Notch IMD W amp F CCIR AO4 AO5 A013 A014 Function LP Audio BP 486 A weight User C mess 80kHz LP LEVEL v v a 2 v3 v3 v3 we L REL v v 2 2 B A 3 THD N v v l 2 v3 v3 v3 s3 NOISE N REL 4 E p eA i are L SEL v v v v v v PHASE 7 z Table 4 Filter Availability ADDITIONAL Function If equipped with the Digital Option order code AO10 the A2 A2 D can offer even more measurement functions which may be very helpful for some applications In this case the corresponding measurement mode may be entered through the lt ADDITIONAL gt key the second function of the lt PHASE gt key Each press to this button toggles between the functions lt PHASE gt and lt ADDITIONAL gt If no digital option is installed the A2 A2 D wil
67. he lt UNIT gt key 3 Select the measurement function to be recorded e g THD N and set the unit for the Y axis by pressing the lt UNIT gt key 4 Choose the start and stop values of the amplitude sweep by setting the generator level to the respective values and pressing the lt START VALUE gt and lt STOP VALUE gt keys 5 Set the generator to the required frequency the output frequency will not vary during the sweep 6 Start the sweep by pressing lt DO SWEEP gt TETI V3 1 om 79 104 User Manual A2 Audio Test amp Measurement System Time Sweep The A2 A2 D offers the possibility to record any measurement function vs time e g to monitor the long term stability of a signal In this mode neither the output frequency level nor any other generator parameter is altered during the sweep See EKT To run a time sweep double click the lt SWEEP MODE gt button cr to open the Sweepmode menu s as Below Time Swp select the gt Seftup entry and push the weepmode lt SCALE gt wheel to open the corresponding submenu Therein you may specify the overall duration of the time sweep gt Tape Freq expressed by a number between 3180 and the dimensions gt Setup Seconds Minutes or Hours Hupp ii cude Make your selection and confirm it by using the lt SCALE gt wheel gt Setup or leave the submenu without a change through the EXIT entry Tableswp EXIT By this way you can specify a time sweep lasting
68. he available modes re gardless of the actual measurement function OE _ The METER mode displays the single results to Witi G R gether with all additional measurement parame D on C oe may be displayed in the GRAPH mode e The SCOPE mode shows the waveform of the input signal in the time domain All these modes can be selected at any time without affecting the actual measurement e g also during a running sweep To increase the lifetime of the backlight of the LC display it is automatically switched Off if no key or wheel on the instrument is used for several minutes However any keypress im mediately re lights the illumination rrer 16 104 om Eii V3 1 A2 Audio Test amp Measurement System User Manual Sweep Operation Sweeps are best performed in the display mode GRAPH that continuously displays the setup parameters and the recorded curve s on the LCD The specific sweep setup may be selected through the keys of the SWEEP block WEEE IAL oop SWORE NCH 9P IN XI O G O O O Fig 3 SWEEP Block Basically there are 5 sweep modes available that can be called through the menu behind the key lt SWEEP MODE gt e Frequency sweeps measure the actually selected function vs a changing frequency e Tape sweeps allow to record a defined frequency pattern on a tape e Amplitude sweeps measure the actually selected function vs a changing amplitude e T
69. he instrument for at least 15 minutes 2 Disconnect all cables from the input and output connectors 3 Activate the A2 Setup menu behind the lt SET REF gt button by double clicking it 357 EF 4 Move the arrow to the entry Calibrate A2 with the lt SCALE gt softwheel ae 5 Confirm the selection by pushing the lt SCALE gt wheel A2 Setup The calibration sequence starts indicating the actual Store Setup step with a message on the display For interpretation of Recall Setu the messages please refer to the A2 A2 D service Recall Default manual The whole procedure takes about two minutes to gt gt Interface measure all the stages Calibrate A2 gt Set Clock gt AutoDetect EXIT If the calibration is aborted with an ERROR message in the display make sure that the unit has been properly warmed up before and re try the calibration Contact your local NTI distributor in case of several failures in a calibration PP 86 104 om Eii V3 1 A2 Audio Test amp Measurement System User Manual Connector Pin Assignment Centronics Connector The CENTRONICS 8bit parallel interface is equipped with a female 25 pin D Sub connector that is fully compatible to PC computers Use a shielded standard Printer cable to connect your printer to the A2 A2 D Printer interfaces Waw va oirik Timing Diagram DATA DoD TA VALIO SIMRE min 0 min ACKNOWLEDSE fai Tiram Primi RS232 Connector The RS232 int
70. ilter 80kHz Lowpass 94 Availability A Weighting C Message 93 Custom Specific 92 External Control Internal Control Synchronization 60 62 Fine Mode Fixed Range Floating Operation PINE eiia aa ai Freeze SCOPE Display 0cce 43 Frequency Front Panel Overview Fundamental Frequency Fuse Mains Power G Gen Status Line Menu Generator Block Diagram wil Frequency 16 31 Frequency Display 35 Frequency Limits Level Level Display User Manual Level Limits Locris asneira 32 Level Unit 36 45 Mute Mute in Crosstalk Mode 0 0 eed 59 Readback Settings Signal in THD N Mode Signals Graph Display Mode Upload to PC X Scaling Graphics Cursor Menu Ground Loop Grounded Operation Erol Ualo Ilale Arne ES H ADP Printe T soreir ianoaiiaea 83 IBM Printe assise eirese 83 IEC IEEE 488 Connector Interface Default Menu Standards Test Signal Impedance Men severe sarees Beets e aeee e aaea Of PPUT iraa of Muted Outputs of Outputs Input Block Diagram Frequency Impedance Level Main Alt Channel ie Instrument Setup 0 eee 85 Interface RS232 IEEE 488 ciccia 14 Internal Notch Filter Synchronization Sweep Synchronization E Synchronization of Narrow BP Filter 59 61 Inventory a J JIS G 55
71. ime sweeps measure the actually selected function vs time e Table sweeps allow to measure the actually selected function vs a previously defined frequency amplitude table requires RS232 or IEEE 488 option Furthermore the lt SWEEP MODE gt key allows to toggle between internally and externally generated sweeps To define the start stop value of the X axis e g 20Hz 20kHz for a frequency sweep set the generator to the desired value and press the lt START gt lt STOP gt key respectively Choose the resolution of your sweep i e the number of samples to be recorded through the lt RESOLUTION gt key Both modes LOW HIGH allow to set the required number of meas urements by entering the sweep resolution menu The recording of a new sweep is started by pressing the lt DO SWEEP STOP gt key while a running sweep may be stopped through the same action Several sweeps may be permanently stored by entering the menu behind the lt GRAPH gt button and selecting one of the four avilable memory locations M1 M3 By this way up to four complete graphs with a max of 6 curves per graph may be stored in the non volatile memory of thze A2 A2 D for a later printout or upload to a PC NOTE This is only a very brief description of the sweep capabilities of the A2 Please refer also to the chapter 6 Sweeps to see all the possibilities tae oe V3 1 om 17 104 User Manual The A2 A2 D User Interface Filfers
72. it is recommended to enter this mode when reading through this chapter Output Parameters The generator frequency output level waveform and output impedance are GEN 1 008k HZ wont gt dBu continuously displayed on the upper i dig Beats two lines of the LC display The top line shows in large characters the set generator frequency and level In the second line the selected output impedance and waveform are indicated as well the actual output voltage readback value or the input impedance of the device under test please refer to chapter Readback for more detailed information Signal Waveform The lt GEN SIGNAL gt key allows to select the signal waveform to be generated It will have either the sine or the ALT symbol illuminated from behind by a green LED To toggle the setting simply push the button once TATA e Inthe mode the generator output will be a SWORE NCI GEN EIGNA oo AI RNI pure sine signal IN XI i D D oa ae actually selected alter The A2 A2 D digital generator offers a wide range of alternate signals To make one of them the active signal double click on the lt GEN SIGNAL gt key This opens the Alt Signal menu showing the list of available alternate signals The active signal is displayed inverted white characters on a ae black background To change the selection move the arrow CS on the left hand side through the lt SCALE gt softwheel to the alternate signal you wish to select
73. ith the Level Selective measurement function the result will rise proportional to the frequency NOTE When analyzing white noise with the level selective function of the A2 A2 D the analyzed amplitude will increase by 10dB decade if plotted against the logarithmic frequency axis A On the other hand pink noise exactly compensates this effect with its constant amplitude vs the logarithmic frequency axis decrease of 10dB decade vs the linear frequency axis evel og Consequently if pink noise is analyzed with the Level Selective function the measured result will show a constant level i gt vs the logaritmic frequency axis T Fequeny llog In practice this effect may be used to evaluate the frequency response of a device under test DUT while being stimulated with a broadband stimulus Prey V3 1 oe 61 104 User Manual A2 Audio Test amp Measurement System To do this simply set the generator of the A2 A2 D to Pink Noise and record a sweep with the Level Selective function the resulting curve will reflect the frequency response of the DUT External Source To control of the center frequency of the bandpass filter proceed in either of the two ways described below 1 Lock the center frequency of the filter to the generator output frequency 2 Let the center frequency synchronize to the dominant frequency of the input signal The locking to the generator frequency has the main advantag
74. k Diagram All output signals are generated by the internal Digital Signal Processor of the A2 A2 D In order to isolate the generator from the analyzer circuitry optocouplers were inserted between the DSP output and the D A converter The analog signal is filtered and fed into the balanced output amplifier Behind this stage an attenuator selects the level range of the output signal The signal is then split to the two output channels and fed through the mute relays The out put impedances are wired behind these mute relays Prey V3 1 om 27 104 User Manual A2 Audio Test amp Measurement System Fig 8 Output Wiring Pin 1 of each XLR output connector represents the center potential between pin 2 signal and pin 3 signal It can either be kept floating or be connected to the chassis ground In general it is recommended to operate the A2 A2 D in the FLOATINGmode in order to avoid ground loops The lt FLOATING GND gt switch is located on the rear panel of C the azva2 D e FLOATING disconnects pin 1 from chassis ground i e the FLOATING g reference potential of the output amplifiers is floating m e GND links the reference potential of the output amplifiers 2 to chassis ground Balanced Operation Normally the A2 A2 D is operated in the balanced symmetric mode In this case the device under test DUT is connected to the two hot pins 2 signal and 3 signal of the generator output stage NOT
75. key will remove filter 1 from the signal path but activate filter 2 and light up the LED be hind UWTD A third press to the lt WTD UWTD gt button deactivates both LEDs indicating that no more weighting filter is active If only one additional filter is installed the UWTD position is not available the lt WTD UWTD gt key will in this case toggle between WTD and Off NOTE The optional filters are handled exclusively if they are activated they automatically switch Off any other active filter Applications The LEVEL measurement is the most widely used measurement function in the Audio field It is useful to e Check the signal level e Line up tape machines e Calculate the output impedance of a DUT out of the level over a certain impedance e Measure the frequency response e Measure the balance between two channels e Calculate the power from the level over a certain impedance To learn more about how to measure a frequency response read chapter 6 Sweeps Overview e The A2 A2 D analyzer provides a bandwidth of 2H2250kHz in the Level mode e The menu behind the lt LEVEL gt key allows to set the unit to either between 1 chn mono or 2 chn stereo measurements e All standard frequency weighting filters as well as installed filter options may be activated e The unit of the generator output level may be altered in the Level measurement mode only rre 46 104 on Eii V3 1 A2 Audio Test amp Measureme
76. l remain in the Phase measurement function ain e Please refer to the AO10 User Manual for further information 3 One filter option may be activated at a time only while both the 400Hz LP and 22Hz 22kHz BP will be de activated 4 Either the 22Hz 22kHz UWTD or CCIR486 WTD filter is active in measurement function NOISE N REL tae ee V3 1 om 67 104 User Manual A2 Audio Test amp Measurement System 6 SWEEPS The A2 A2 D is not only capable to measure single values but also has a built in set of pow erful sweep capabilities that enable the user to record complete graphs in a few steps Following sweep modes are supported allowing to record almost all available measurement functions of the A2 A2 D against various parameters e Frequency sweeps internally controlled by the generator e Frequency sweeps controlled by an external source e Frequency sweeps controlled by the generator with av fixed interval per step tape sweeps e Amplitude sweeps controlled by the generator e Time sweeps e Table sweeps where discrete sets of frequency level pairs are stored in the internal memory of the A2 A2 D requires RS232 or IEEE interface option All these sweep types can be performed at either LOW or HIGH resolution number of sam ples between the start stop values Pleas notice that not all measurement functions can be swept in all available modes e g W amp F cannot be s
77. l the necessary information and results of the selected measurement task and all related information which may further help to qualify your measurements The top line s always contains the generator parameters and the bottom line is reserved for the input parameters GEN 1 00kHz 14 5dBu Out 2682 Sine m 10 4dBu B 16 4dBu 2 CHN coe 5 55dqdBu cm 14 4dBu 5 66dBu 5 68dBu DIU 26 6dBu B 1 66kHz 5 55dBu E 1 660kHz 14 4dBu Fig 13 METER Panel Please notice that the METER display will automatically change its layout for all 1 channel measurement by showing the single measurement result in large letters instead of the two lines of the 2 channel Level result Prey V3 1 om 33 104 Pre Ty 34 104 om Eii V3 1 A2 Audio Test amp Measurement System User Manual Generator Settings The selected generator output voltage nominal value and frequency are always displayed on the top of the METER display The unit in which the frequency is expressed cannot be influenced by the operator while the unit of the generator output voltage is the same as selected for the Level measurement results Please refer to chapter Output Section Output Parameters for more details about the generator settings NOTE If the generator signal is set to White or Pink Noise the frequency of the generator is still displayed although a noise signal obviously has no frequency However the assignment of a generator frequency is necessa
78. lt SCALE gt wheel increases the sensitivity units division of the bar graph e ACCWincrement decreasesthe sensitivity i e it enlarges the displayed range e A fast turn of the lt SCALE gt wheel in the CW CCW direction sets the scale of the bar graph to the highest lowest sensitivity respectively If the bar graph is zoomed the center value is kept constant if possible symmetric zooming However in case that the value 0 zero would fall into the scale it is shifted to the left border value of the new scale Scrolling the Bar graph The SCROLL mode may be entered by pushing the lt SCALE gt softwheel once from the ZOOM mode or twice slowly no double click from the AUTO mode It allows to scroll the visible range of the bar graph scale through the availbale range e Every incremental step of the lt SCALE gt wheel in CW direction moves the visible part of the bar graph to the rightby one division e On the other hand a CCW increment moves the visible part of the bargraph to the eft To quickly locate the range where the signal is located in the bar graph make a fast turn of the lt SCALE gt wheel in CW or CCW direction This acts like a beam finder Turn CCW if the signal is larger than the displayed scale or CW if no signal is visible at all To set the scaling function back to AUTO mode push the lt SCALE gt wheel twice quickly The actually selected mode AUTO ZOOM or SCROLL is always indicated by a LED b
79. ltmenu by double pressing the lt IMD gt button We The menu shows a list of the two low frequencies 60Hz and IMD Default 250 Hz and the three amplitude ratios 1 1 4 1 and 10 1 IMD6O 1 1 Use the lt SCALE gt softwheel to move the arrow to the re r quired selection and push the wheel once to activate the IMD250 1 1 selection The menu closes automatically after the selection IMD250 4 1 n IMD250 10 1 To leave the menu without altering the current signal select EXIT EXIT or press any other key pippe V3 1 bie ff 53 104 User Manual A2 Audio Test amp Measurement System Unit The IMD measurement result may be expressed either in dB or selected through the lt UNIT gt button Filters As shown in Fig 20 the IMD measurement requires a special demodulation circuit and fixed filters All these filters are set automatically when activating the measurement function IMD Consequently no other filters are allowed to be used for IMD measurement thus the whole filter bank is disabled Applications Intermodulation distortion measurements are of advantage in comparison to THD N meas urement especially in the higher frequency range where a THD N measurement requires a fairly large bandwidth Furthermore the stimulation of a DUT with two in parallel comes closer to the reality than a single sine stimulus IMD test are often used to characterize the non linear distortions of amplifiers mixers com pressors etc r
80. must correspond to the Tape Sweep described in the pre vious chapter In the external sweep mode the analyzer will synchronize its tracking filter to the incoming signal The recording external sweep will be started through a steady 315Hz or 1kHz tone being present for at least 3 second and followed by a decrease of the frequency This start condition complies with the international standards for test tapes Preparing an External Sweep 1 Set the A2 A2 D in the GRAPH display mode and select the measurement function you want to record 2 Open the Sweepmode menu behind the lt SWEEP MODE gt key and select Frequency Set the synchronization to EXT by pressing the lt SWEEP MODE gt key 4 Choose the start and stop frequency of your sweep as described chapter Setting the Sweep Limits 5 Open the Resolution menu behind the lt RESOLUTION gt key and enter the expected number of sweep samples This value is used by the A2 A2 D to calculate the frequency increments This logarithmic frequency increment is calculated as follows w log fStart log fStop log Af ALl NOTE In the external sweep mode the A2 A2 D will record exactly the number of points defined through the Resolution menu Even in case that the external source provides a higher resolution i e a higher number of frequency steps the instrument will perform a measurement only if an incoming frequency equals the expected one or is higher than it 6 Conne
81. n 3 of both output channels independ ently from the active analyzer function The readback measurement reuslts are displayed on right hand side of the status line in the METER display mode Alternatively it is possible to show the load impedance R of the de vice under test with an accuracy of 5 1 Q METER To select whether the readback voltage or the load imped ance of the DUT shall be displayed open the Gen Status i Line menu by double clicking on the lt METER gt button Gen Status Line Next make your selection by turning the lt SCALE gt soft wheel to the respoective position and pushing the wheel gt Read Voltage once Read Impedance EXIT NOTE The reading of the load impedance is most accurate if the selected source impedance is closest to the displayed load impedance rrem 32 104 om Eii V3 1 A2 Audio Test amp Measurement System User Manual Consequently the displayed values of the second line in the METER panel can be summa rized as follows 1 The selected output impedance 2 Theactual waveform 3 The true output level input impedance of the DUT of both channels Output Muting O On the right hand side of the output connectors AA N are the lt MUTE gt buttons that allow to switch Off ER the generator signal oA If activated the mute function internally discon iC nects the generator from the output connector and inserts a short circuit behind the imped ances see
82. n input channel Provides Windowing functions Zoom amp Scroll of axis as well as direct printouts AO13 C Message filter The filter may be activated with the lt WTD UWTDs gt key For 2 chn measurements two filters are required A014 80kHz lowpass filter The filter may be activated with the lt WTD UWTD gt key For 2 chn measurements two filters are required AO15 Update software package from AS03 to AS04 Utilizes the ASO3 interface AO16 High speed RS232 interface with Windows based software package AS04 Allows the remote control of all analog and digital functions of the A2 or A2 D Provides additional features thus enhancing the performance of the instrument The included easytotearn Audio Measurement Programming Language AMSL allows to write sequences and PASS FAIL tests for automated applications Supports conversion of ASO3 AMSL programs Demo disks available FETI V3 1 oe 89 104 User Manual A2 Audio Test amp Measurement System RS232 Serial Interface AO1 AO16 Both options comprise the hardware board to allow the physical communication according to RS 232 and either the software package ASO3 or AS04 Both packages come on 3 HD diskettes with separate User Manual e The ASO3 allows to comfortably control all analog functions of the A2 Requires a MS DOS PC with 286 processor or higher e The Windows based AS04 software package is able to control all analog and digital features
83. nal Please refer also to the block dia gram shown in Fig 4 The bandwidth of the A2 A2 D analyzer is limited to 2Hz 250kHz while the allowed input level ranges from 1uV to 200Vams MEASUREMENT TO enter the Level measurement function make Leve HN sure that no sweep is running and press the om I Bent the A2 A2 D will show the meas an ured input level s on its LCD Should the display Bea ware show L REL then press the lt LEVEL gt key once again to enter the absolute level measurement mode labeled 2 CH or LEVEL Mono Stereo Measurements The lt LEVEL gt key hides the Level Display menu that allows ovi MEN the operator to choose between 2channel stereo or single z channel mono level analysis hu wo This menu can be opened by a double click to the lt LEVEL gt button Use the lt SCALE gt wheel to move the arrow to the re quired mode 1 2 Channel A push to the lt SCALE gt wheel activates the selection while any other ley leaves the menu 1 Channel without a change gt Pi a EXIT Level Display The bottom line of the METER display shows the RMS level s and the frequency of both input channels A and B measured right behind the input connectors i e the not filtered input signal s Please refer to chapter Input Display for further information Units The A2 A2 D provides the possibility to express the Level measurement results in several units The linear unit V repres
84. nal is fed to the alternate channel tae oe V3 1 oe 21 104 User Manual A2 Audio Test amp Measurement System Input Block Diagram Fig 4 Block Diagram Analyzer Input Wiring amp Impedances Both input channels are fully balanced and terminated with defined impedances right behind the input connectors Threesettings are available ene e The highest possible impedance terminates the inputs with 100k corresponding a voltage matching by means of a minimum load to the output of the device under test e The second value 6002 is intended for all in struments with this output impedance e The low input impedance can be set to 150Q or sa 2002 Choose one of these three settings by pressing the lt IMPEDANCE gt button Each keypress will toggle to the next impedance The actually selected impedance is displayed on the left hand side on top of the METER panel NOTE As soon as a level of more than 20V is applied to one of the inputs the LOW and MEDIUM impedance selections will be disabled automatically to protect the inputs from being destroyed An alert message will inform you accordingly in this case If the LOW impedance is activated NEVER apply an input voltage gt 60V since higher voltages can permanently destroy the electronics Pro Ty 22 104 on Eii V3 1 A2 Audio Test amp Measurement System User Manual The figure below shows the simplifi
85. nctions comprises a specific tracking filter i e a notch or bandpass filter with variable center frequency that must be synchronized to the generated frequency Table 5 provides an overview over the available synchronization modes for internally and externally controlled sweeps Sweep Type Internal Control External Control Frequency Sweep Yes Yes Tape Frequency Sweep Yes Yes Amplitude Sweep Yes No Time Sweep Yes Yes Table Sweep Yes No Table 5 Sweep Synchronization Modes rey 70 104 Ln is Eii V3 1 A2 Audio Test amp Measurement System User Manual To set the sweep mode toexternal synchronisation set the lt SWEEP MODE gt button to EXT In this mode the tracking filter and the sweep measurements are controlled by the frequency counter of the active A2 A2 D analyzer channel In position INT the control of the sweep and the tracking filter is done by the NT ENT internal oscillator of the A2 A2 D This mode is much faster than external sweeps since both the tracking filter D k and analyzer get the frequency information directly from the generator Please refer also to chapters Frequency Sweep and Tape Sweep for further information Sweep Recording Keep a Recorded Trace To keep a recorded trace on the screen open the Graphics menu by double clicking to the lt GRAPH gt button in the GRAPH display mode Move the arrow to the entry Keep Sweep and confirm by using the lt SCALE gt softwheel basil Conseq
86. nt The signal to noise ratio S N generally expressed in dB reflects the ratio of the RMS Voltage of the wanted signal to the coexistent noise in a transmission channel 1 Set the analyzer to measurement function L REL expressed in dBr Connect the A2 A2 D output to the input of the DUT and apply the wanted signal Mute the output of the generator or DUT in order to receive the noise signal only Press the lt SET REF gt key De mute the output of the generator DUT The displayed measurement result corresponds to the signal to noise ratio expressed in dB OF eI NOTE Do notuse the Noise function to evaluate the signal to noise ratio since this mode measures the quasi peak weighted noise instead of the RMS voltage as required for S N measurements rrem 48 104 om Eii V3 1 A2 Audio Test amp Measurement System User Manual THD N Function The A2 A2 D measures the Total Harmonic Distortion plus Noise THD N of the active channel by inserting a band reject notch filter into the signal path This notch filter is tuned to the frequency of the main component of the input signal i e the fundamental frequency Thus the fundamental frequency is removed leaving everything else i e the harmonic dis tortion and noise for the measurement The result of this measurement is compared to the level of the incoming signal and expressed in percent or in dB A J Fucclarsac 8 7 i larmories i z al
87. nt System User Manual Level Relative Function The Level Relative function is an extension of the bsolute Level measurement function allowing to change the reference voltage for the Level measurement i e to measure the in put level relatively to a user defined reference To activate the Level Relative measurement function make sure that no sweep is currently running enter the Level mode and press the lt LEVEL gt key a second time Doe NRI es CE NOTE Every push to the lt LEVEL gt keys toggles between the two measurement functions Level and Level Relative As soon as you have activated the Level Relative mode L REL will be displayed on the LCD and the A2 A2 D analyzer will immediately show the actual result On the bottom line of the METER display the absolute input level and frequency of the active channel as well as the current reference level are indicated All Level Relative measurements are made against this reference To set or change this reference value apply the reference voltage you require to the active input channel and press the lt SET REF gt key on the upper right corner of the front panel MEASUREMENT FUNCTIONS IPV IH IN Not GUIE AI lt Br R Fr lt vo NREL Atel care F OR a E The new reference level will be active and displayed immediately on the bottom line of the METER dis
88. o adjust the mains power requirements The A2 A2 D2 can operate from 100VAC 120VAC 230VAC or 240VAC To configure the input line voltage of he A2 A2 D remove the mains cable and open the flap of the connector fuse holder assembly at the rear panle of the A2 A2 D by pressing a small screwdriver into the slot on the top or ruin your fingernails tae oe V3 1 oe 13 104 User Manual A2 Audio Test amp Measurement System Take out the drum and insert it in the new required position The label pointing towards the operator indicates the selected line voltage At the same time insert a new fuse with the proper current rating must For 100VAC and120VAC a 2A fuse has to be used while for 230VAC and 240VAC a 1A fuse is required After having set the required line voltage and installation of the proper fuse close the flap and insert the power cable The A2 A2 D is designed to be connected to protective ground earth through the ground wire in the power cable This connection is essential for safe operation NEVER operate the instrument if the safety ground connection is not available or has been compromised Printer Connection The CENTRONICS printer connector is located at the rear panel of the A2 A2 D It is a 25 pin female D type connector the same as installed in a standard PC To select the required printer driver please refer to the chapter 7 Printouts The appendix describes in detail the pin assignment
89. o Test amp Measurement System was designed to be connected to a specified mains power source with safety grounding through an approved three wire mains power cable NEVER operate the instrument with missing or compromised safety ground connection e To avoid fire hazard the mains power fuse of the A2 A2 D must be replaced in case of failure by a fuse with the correct rating see chapter 2 Installation e For safety reasons never apply voltages higher than 200Vkms or 300Vp to the measurement inputs of the A2 Voltages higher than that may permanently destroy the internal electronics e There are no parts inside the instrument that may be repaired or replaced by the user Therefore never open the unit for any reason Overview The NTI A2 is a comprehensive high performance two channel audio test set It includes a flexible generator based on a Digital Signal Processor DSP and a high performance analyzer providing a wide variety of measurement functions as there are e Level absolute two channel in uV mV V dBV and dBu or dBm e Level relative in 1 and dBr e Level selective in uV mV V dBV and dBu dBm e Total harmonic distortion amp noise THD N in and dB e IMD Intermodulation distortion in and dB e Wow amp Flutter in e Noise absolute weighted and unweighted in Vq mVq Vq and d Bq e Noise relative weighted and unweighted in 1 and dBr e Crosstalk frequency selective in 1
90. of the A2 or the A2 D under a minimum configuration of a 486 CPU with co processor Windows 3 1 or higher and 8MB RAM The serial interfaces have the following communications parameters AO1 A016 Protocol AS03 AS03 AS04 Selectable baud rate 2400 4800 9600 9600 19200 38400 Data bits Stop bits Parity An upgrade package from AS03 to AS04 comprising the software upgrade only is also available Baudrate Selection To select the communication protocol and the baudrate communication speed of the serial interface open the Baudrate menu behind the lt SET REF gt key and select the entry gt Interface Depending on the installed interface AO1 or ea AO16 the submenu menu offers the available baudrates and protocols The example is shown for z the interface AO16 providing the three baudrates Baudrate 1 setup 9600 19200 and 38400 baud as well as both the 2600 Baud setup AS03 and AS04 protocol 19200 Baud Setu Default To alter the selection move the arrow with the gt terface lt SCALE gt wheel to your new choice and push the EXIT ate A2 wheel to make the selection active piest E Leave the menu without a change through the EXIT entry or any keypress The connection to the PC is performed through a female 9 pin D Sub connector For pin layout and description see chapter RS232 Connector rre 90 104 om Eii V3 1 A2 Audio Test amp Measurement System Filter Options
91. om 41 104 User Manual A2 Audio Test amp Measurement System SCOPE Display Mode The SCOPE mode extends the set of A2 A2 D tools by offering a simple audio oscilloscope that lets the operator analyze the waveform of the input signal s in the time domain To enter the SCOPE mode simply push the lt SCOPE gt button Consequently the LC display will change to the oscilloscope mode and show the input signal s vs the time axis THD N GEN 1 259kHz 9 831 U 164 us DIU Fig 17 SCOPE Display Example On top of the LCD the generator level and frequency are indicated like in the other display modes Below the waveform s are plotted whe reof the A2 A2 D automatically determines the scaling of the Y measurement function and X time axis i e there is no possibility to set the scaling manually e Both resolutions are displayed next to the corresponding axis to allow to read out accu rately the amplitude and period Minimum time resolution is 10s per division e f possible the auto scaling displays one period of the signal This ensures that the op erator can qualify the waveform of the input signal without the need to modify the set tings In the 2 channel Level mode the sensitivity of the Y axis is identical for both channels and determined by the level of the active main channel Optimized scaling for the alternate channel can be obtained by making it the active channel push the lt A
92. om 95 104 User Manual A2 Audio Test amp Measurement System 10 TECHNICAL SPECIFICATIONS Analog Generator Signals Pure amp Warbled Sine Symmetric amp Asymmetric Squarewave Triangular Wave Pink amp White Noise IMD Testsignals see IMD Frequency range 10Hz 100kHz for Sine signal 10Hz 20kHz for Squarewave and Noise 20Hz 40kHz for Warbled Sine 4kHz 40kHz for IMD Signal Frequency Resolution lt 0 05 Frequency Accuracy 0 01 of defined value Output Level 10uV 24 5Vrms 100dBV to 27 7dBV Level Resolution lt 0 05 dB Level Accuracy 0 c 0 5 of defined value Flatness 0 05 dB 20Hz220kHz Ref 1kHz 0 05 typ Output Impedance lt 159 150Q 200Q 6009 Residual THD N typ 94dB 0 002 lt 90dB max or 10V 20Hz 20kHz unloaded DIN audio BP Square wave rise amp fall time lt 5us unloaded IMD Signal f1 60Hz or 250Hz f2 4kHz 40kHz ratio 1 1 4 1 10 1 sweeptable Digital Generator Output Format Professional according AES 3 and Consumer according IEC958 optical TOS link Impedance 1100 759 Sampling Frequency 32kHz 44 1kHz 48kHz or input clock or analyzer clock Frequency Accuracy 10ppm 2ppm on request Detune 1500ppm Resolution 4 24bits Dithering TPDF switchable Jitter Generation 2 40ns with selectable modulation signal Output Level 0 15 5Vpp Trigger Output X Y Z Preamble Bitclock Sweep Function Modes Frequency Amplitude Time amp Tablesweeps over entire
93. omatically by the A2 A2 D The unit of the measurement function Y axis may be selected through the lt UNIT gt button Each press to this key steps through the available units NOTE When changing the unit the A2 A2 D does not repeat the sweep meas urements but re calculates the recorded traces even during a running sweep recording This allows for example a quick conversion from any linear scale to a logarithmic scale and vice versa Pre Ty 38 104 om Eii V3 1 A2 Audio Test amp Measurement System User Manual Cursor Function After having recorded a Frequency Amplitude or Table sweep it is possible to activate a cursor to read out the individual measurement results of the curve This allows to display all result pairs that are part of a sweep curve In practice the lt FREQUENCY gt lt LEVEL gt softwheel respectively allow to control the posi tion of the cursor e To activate the cursor in a Frequency or Table sweep simply set generator frequency into the range of the recorded sweep X axis by using the lt FREQUENCY gt softwheel Consequently a crosshair becomes visible in the graph representing the cursor On the bottom line of the graph the frequency amp measurement function results corresponding to the position of the crosshair are displayed in inverse letters white on black e For Amplitude sweeps the cursor is available by setting the generator level into the range of the recorded sweep X
94. our complete graphs can be stored in the internal memory of the A2 A2 D Please refer to the following chapters for further details Selecting the Sweep Mode The A2 A2 D is able to perform several sweep types They can be chosen from the menu behind the lt SWEEP MODE gt button refer to chapter Sweep Modes for further details Pc Ty 68 104 V3 1 A2 Audio Test amp Measurement System User Manual ee EKT Activate the Sweepmode menu by a double click to the lt SWEEP MODE gt button The arrow in the menu can be moved v to the required entry with the lt SCALE gt wheel Confirm your selection by pushing the wheel once Swaepmode Some entries like Tape Freq and Time Swp have a further Frequenc menu behind that allows to define some more parameters of the gt Tape Freq specific sweep type The detailed explanations of these pa gt Setup rameters are given in the description of the corresponding Amplitude sweep t Time Swp P type a gt Setup The menu closes automatically after the confirmation Selection Tableswp of the entry EXIT or any keypress will close the menu without EXIT any change Setting the Sweep Limits amp Resolution In the sweep modes Frequency and Amplitude the limits of the sweep can be chosen freely in the range of the internal generator D2 SVEE RESO UT CN START TI 2WEE MODE CEN SIS A 70 CN ICH VA UE VANE NT EXT Aa AT O O c C Coy Pa
95. outputs of the A2 A2 D to the inputs of your tape recording machine Next execute the following steps 1 Enter the GRAPH display mode and set the start amp stop frequency as well as the resolu tion The required time for the whole sweep is determined by the number of steps multi plied by the time interval NOTE In some measurement functions the allowed frequency band is limited due to physical reasons For instance IMD measurements are not al lowed to be measured below 4kHz In these cases the generator will not exceed the allowed range eee EST 2 Open the Sweepmode menu by double clicking to the lt SWEEP MODE gt button Select the gt Setup line push aT lt SCALE gt wheel once A sub menu will open to allow the definition of the step Sweepmode interval in the range of 0 5s 1s 2s 10s The fastest possible setting strongly depends on the selected measurement function as well as the quality and stability gt Tape Freq of the recording Push the lt SCALE gt wheel to confirm gt Setup your selection Amplitude The bottom line of the LCD shows the mode Tape and tS Setul the selected speed as e g 3 0s Step TableSwp EXIT rents V3 1 Linii i 75 104 User Manual A2 Audio Test amp Measurement System 3 Set the generator to 1kHz and to the desired output level The 1kHz tone is required to identify the header of the sweep i e to allow the sweep to start automatically 4 Set the tape ma
96. p F gt WEF Move the arrow to the standard of your choice by turning the lt SCALE gt wheel and confirm by pushing the wheel Alterna TEC DIN tively leave the menu through the EXIT entry or by pressing NAB JIB any key 3 00 kHz f ENCETMI Any time you enter the W amp F functi on now the last selected EXIT standard is applied Furthermore it is displayed right of the W amp F sign on the METER display The generator is automatically set to the selected frequency in the W amp F mode When switching to another measurement function e g Level the generator frequency is set back to the previous value This intelligence allows e g to execute very quickly a Level meas urement at 1kHz switch over to W amp F at 3 15kHz and then measure THD N at 1kHz without the need to access the generator frequency W amp F Measurements Replay only For this measurement method you need a standard W amp F test tape 1 Connect the replay output of the recorder under test to the active input of the A2 A2 D Load the standard wow and flutter test tape Make sure that the settings of the frequency corresponds to the test tape 2 Press the lt W amp F gt and lt METER gt buttons One of the LEDs over the lt WTD UWTD gt button will be lit indicating either the weighted W amp F filter active or unweighted audio bandpass filter active mode Select the appropriate filter through the lt WTD UWTD gt key 3 Start the tape in the replay mode
97. play Keep in mind that the generator level displayed continuously in the top line of the display is always measured in absolute terms Filters For the Level Relative function the Audio bandpass 22 4Hz 22 4kHz as well as the 400Hz highpass filter are available in any combination Furthermore all installed optional weighting filters can be activated as well Select the filters by pressing the corresponding key FETTI V3 1 om 47 104 User Manual A2 Audio Test amp Measurement System ee FR Wi Wet Jaane S pezeN UNI em A os O Voc Ba Ganon Units As with the absolute Level function several units are available for Level Relative measure ments They can be selected through the lt UNIT gt button Each press toggles to the next available unit Unit lin log Reference Calculation A lin UREF UWI 4 100 Urer V 4 lin Use IV Urer V dBr log Urer log avi aa or U dB Use dB Table 3 Level Relative Units Application Example To measure the channel balance in a stereo equipment proceed as follows 1 Apply the signals to the inputs of the A2 e g left chn to input A right chn to input B 2 Select with the lt A B gt key the reference channel which is usually left e g input A 3 Push the lt SET REF gt button then make the other input channel the active one press the lt A B gt key 4 The channel balance can now be read out directly Signal to Noise Measureme
98. pole tracking bandpass Q 5 Psophometric Filter A weighted according IEC 651 optional Display of A2 A2 D 256 x 128 dot backlit graphics LCD module Measurement display with large 15mm numeric values and two 100mm Bargraphs Interfaces Centronics compatible parallel printer port 25pin Sub D for graphics and text printouts Supports Epson FX and LWQ IBM Proprinter HP Deskjet Thinkjet and Laserjet printers RS232 serial port optional for remote control and data transfer between A2 and IBM PC compatible computer IEEE 488 parallel remote control interface optional for remote control and data transfer between A2 and PC BNC monitor outputs offering both input channels and reading signal level typical 3Vpp Rout 600Q General Data Dimensions 274 x 396 x 132mm 11 x 15 x 5 Weight Approx 9kg 20lbs Fab Requirements 100 120 230 240VAC 50 60Hz 85VA Temperature Range 0 45 C 32 113 F Humidity 10 90 R H non condensing erent V3 1 HEE 99 104 User Manual 11 INDEX a A A2 Setup Menu Accessories Alt Input Channel Monitor Output Signal Menu Signals Alternate Amplitude Sweep AOx Options Auto Range Scaling of Bar graph Scaling of Sweep Graph Backlight isaisip inaire usea Balance of Input Channel Balanced Connection Operation Band Reject Bandpass Filter A2 Audio Test amp Measurement System Input S
99. r the sweep characteristics to the specific demands of the DUT or even to define a de emphasss curve as output signal for a sweep The definition of a sweeptable has to be done externally of the A2 A2 D on a PC It may be downloaded to the instrument either through the serial RS232 or parallel IEEE interface For this purpose both the DOS based AS03 and the Windows based AS04 software package provide the possibility to define and send sweep tables to the A2 A2 D In this way sweeptables can be defined in a te xtfile format extension SWT and stored in the non volatile memory of the A2 A2 D Each sweep table may comprise an eight character string for identification This string is shown on the LCD of the A2 A2 D as soon as the table sweep mode is activated The time amp date of the last downloaded sweeptable is displayed in the bottom line of the GRAPH display when the arrow in the Sweep Mode menu is positioned besides the entry F Tab Swp Sweep Data Upload to a PC With the aid of the software packages AS03 AS04 it is also possible to upload all stored graphs from the A2 A2 D to a PC The data are available both as tables and as graphics and may be exported to other PC programs For further details please refer to the AS03 AS04 User Manuals tae ae V3 1 oe 81 104 User Manual A2 Audio Test amp Measurement System 7 PRINTOUTS Implemented as a standard feature the A2 A2 D allows to print out the screen contents in
100. re 54 104 on Eii V3 1 A2 Audio Test amp Measurement System User Manual Noise Function The Noise function of the A2 measures noise according to the CCIR Recommendation 468 3 and 468 4 in either absolute or relative terms The signal path in the Noise function includes either the Audio bandpass filter or the weighting filter defined in the above standard The in ternal rectifier of the A2 A2 D always measures Quasi peak in function Noise The Quasi peak rectifier is a RC network that has a very short attack time but quite a long decay time This type of rectifier especially weights the spikes in the noise signal so that the result corresponds closely to the audibility of the signal Nevertheless some applications e g signal to noise ratio require to measure noise RMS rectified maybe even with a specific weighting filter The A2 A2 D can also perform these measurements in the LEVEL function with the corresponding filter e g Aweighting To perform a Noise measurement apply the signal to be measured to the active input con nector and press the lt NOISE gt key VE HYN CRO TAIK e K 7 ad IND L Sse m OSPA MODE z Bi TR Each further press to the lt NOISE gt button will toggle between the absolute and relative Noise measurement function denoted by NOISE and N REL in the display Select NOISE for absolute measurements The METER display shows the result together with the w
101. re the THD N of signals below 250Hz with the 400Hz high pass filter being enabled since the second harmonic would not be measured in this mode NOTE To characterize the dominant type of distortion enter the display mode SCOPE The second trace in hat display shows the residual distortion signal Check for any correlation to a harmonic or hum etc Units The THD N measurement as well as the SINAD measurement described below are relative measurements The units available are therefore the linear percent scale and the loga rithmic decibel dB scale that may be activated through the lt UNIT gt key ac eae ae 50 104 om Eii V3 1 A2 Audio Test amp Measurement System User Manual SINAD Measurement The A2 A2 D is also capable of measuring the SINAD value although there is no special key provided for this function This is because of the SINAD function being very closely related to the THD N function The THD N value quantifies the distortion of the signal while the SINAD value expresses the purity of the signal Distortion Noise Signal Distortion Noise THD N __ and SINAD Signal Distortion Noise Distortion Noise From that follows SINAD and SINAD dB THD N aB THD N Equation 2 SINAD Calculation From these equations we can see that the SINAD value is the reciprocal value of the THD N e f expressed in a logarithmic unit dB the
102. red U inactive Filters The Crosstalk measurement automatically inserts the narrow bandpass filter see Fig 22 into the active analyzer path FETTI V3 1 om 59 104 User Manual A2 Audio Test amp Measurement System xTALK Filter orf Input f Qutput 1 000 U 20 04kHz 20 00 Hz Frequency log 2 0 kH2 Fig 22 Narrow Bandpass Filter Characteristics Furthermore in order to limit the measured bandwidth and or to reject hum components in the measurement signal the standard filters 400Hz HP and audio BP may be activated External Source The A2 A2 D is also capable to measure the Crosstalk from any external source like a CD player or a test tape instead from its own generator The only difference to the previously described method is that the tracking receive filter has to be controlled and tuned to the in put frequency instead of the internal oscillator F This can be done by pushing the lt INT EXT gt button Va u Va ue ance so that the LED behind the EXT sign lights up 7 7 The rest of the procedure is exactly the same The track C IC IC or tape with the test signal has to be fed to the inactive input channel while the quiet channel is fed to the active one NOTE It is advisable to measure Crosstalk not only from chn A to B but also from chn B to A There might be noticeable differences in the results Pro Ty 60 104 om Eii V3 1 A2 Audio Test
103. ry to set the tunable notch filter of the A2 A2 D to the desired frequency Generator Readback In case of a relatively low input impedance of the device under test DUT the true output voltage of the A2 A2 D generator may be lower than the selected and displayed nominal level Therefore an additional readback reading of the true output voltage or alternatively of the input impedance of the DUT is permanently displayed Please refer to chapter Output Section Readback for further details VETER Open the Gen Status Line menu by double clicking to the lt METER gt key Therein one may toggle the display be H tween the readback voltage and the load impedance of the Gen Status Line DUT by using the lt SCALE gt softwheel gt RET RALECS Please note that in measurement function IMD the read Read Impedance back feature is disabled Measurement Results The results of the selected measurement function are displayed in both numerical and ana log form through large digits and a bar graph below In the 2 channel Level measurement mode two lines of both display forms are placed on top of each other All measurements results except of noise are true RMS values Noise is measured quasi peak according to the CCIR 468 3 standard NOTE The input and the readback voltage are always RMS values independent of the selected measurement function Units The unit in which the result shall be expressed can be selected b
104. ser Manual It is strongly recommended to save the original cardboard box for the case that it ever becomes necessary to ship the A2 A2 D Never ship the instrument in a box not properly protecting the unit against mechanical shock since the NTI warranty does not cover damages caused by improper packing Options and Accessories Besides the wide range of already builtin features of the A2 A2 D there are some optional items available for the A2 A2 D as listed in chapter 8 Instrument Setup Please ask your local NTI agency for further details Environmental Conditions The A2 A2D test system will operate in accordance with its specifi cations as long as the envi ronmental conditions are kept within the following ranges Temperature 5 45 Celsius Humidity 10 90 non condensing Mains Power Supply After having unpacked the unit it is first necessary to connect the system to the AC mains power of your country For this purpose the enclosed mains power cable has an uncon nected end with three colored leads corresponding to Brown Live Blue Ground Green Yellow Earth Attach a mains plug to this end of the cable fitting to the receptacles of your area Next make sure that the mains power voltage matches the power selection that is shown on the mains power connector fuse holder assembly on the rear panel of the A2 A2 D If this selec tion is incompatible with the available power source go through the following paragraph t
105. sofwheel in clockwise CW counter clockwise CCW direction zam EGALI e Every incremental step of the lt SCALE gt wheel in CW direction cane moves the visible range down by one division e A COW increment of the lt SCALE gt wheel lowers the curve by NT one division lensi The borders of the actual range Min amp Max values are always displayed on the left hand side of the graph NOTE A fast turn of the lt SCALE gt wheel in the SCROLL mode acts like a beam finder i e lets the A2 A2 D display any recorded curve that is located ei ther below CW turn or above CCW turn of the actual position X Scaling After having recorded a sweep the scaling of the X axis Min Max values may be changed To do this set the parameter of the Xaxis by turning the corresponding softwheel to the de sired value and press the lt START VALUE gt gt STOP VALUE gt key respectively e In a recorded Frequency sweep use the lt FREQUENCY gt softwheel e In a recorded Amplitude sweep use the lt LEVEL gt softwheel Gi SWEE ABS OUT CN ART ATAS WEE MZE CEN KNAL iton W ICH VALLE VAME NT EXT Ow ALT Cy CO A Ca Oo Va Consequently the graph and all recorded curves are re drawn automatically in the new range In other terms the curves are not measured again but fitted into the new graph Refer also to chapter 6 Sweeps for more information ta a oe 40 104 on V3 1 A2 Audio
106. t out the A2 A2 D automatically freezes the scope screen The operator can release this freezing mode by a double press to the lt SCOPE gt button to watch the trace even during the printout but with the side effect of a slower printout In the THD N mode only the residual is printed out See also chapter 7 Printouts for details about printer settings LEVEL Filter Off Input 0 26dBu 630 7 Hz Output 0 21dBu 630 7 Hz 500 0mv per DIV 200 0us per DIV Fig 18 Example of a Printout in the SCOPE mode Overview e The SCOPE screen displays the waveform of the input signal s in the time domain e The scaling of the X amp Y axis are set automatically i e cannot be changed manually e Inthe THD N measurement function the unfiltered input signal as well as the distortion residual are displayed simultaneously e If the Noise measurement function is active the SCOPE mode is not available pippe V3 1 om 43 104 User Manual A2 Audio Test amp Measurement System 5 MEASUREMENT FUNCTIONS Level Function The Level measurement function allows to perform an absolute level amplitude measure ment in true RMS for either one channel or two channels simultaneously After having passed the input amplifier attenuator stage the input signal is rectified by the true RMS detector and A D converted for further analysis Additionally several filters may be intro duced into this path in order to further weight the sig
107. tch on the rear panel accordingly e Double clicking to the lt A B gt key opens a menu to select either Auto or Fixed ranging e The monitor speaker reflects input signal after the input stage and filtering Its volume can be controlled through the potentiometer on the front panel e The READING output monitors the input signal after the input and filter stage e The MAIN CHANNEL and ALT CHANNEL connectors provide the normalized but unweighted input signals PP 26 104 om Eii V3 1 A2 Audio Test amp Measurement System User Manual Output Section The A2 A2 D is equipped with a versatile digital generator providing optimum performance with maximum flexibility to supply the device under test with purest signals The most important features of the generator are e Output level 100dBV to 27 6dBV 10uV 24 5Vams e Frequency range 10Hz 100kHz e Selectable output impedances lt 15Q to 600Q e Seven different signal waveforms Very pure sine signal with typical THD N lt 91dB lt 0 001 Warbled sine signal IMD signal according to SMPTE and DIN Squarewave duty cycle 50 50 or 40 60 W amp F signal according to IEC and NAB White noise Pink noise e Fast parameter setup through function keys and softwheels e Individual mute function for each channel e Sweep capability over the entire frequency amp level range Output Circuit The diagram below shows the simplified diagram of the A2 output stage Fig 7 Generator Bloc
108. te the Signal to Noise ratio The reason is that the Noise mode of the A2 A2 D measures according to the CCIR standard peak weighted while for the S N ratio a RMSweighted measurement has to be executed see p 48 p p i oge g 56 104 om Eii V3 1 A2 Audio Test amp Measurement System User Manual Noise Relative Function In opposition to the absolute Noise function that measures against the fixed reference of OdBq 0 775V the Noise Relative mode allows to make any input signal the reference level To perform a Noise Relative measurement push the lt NOISE gt button until N REL appears on the LCD e DEPLAYMODE pre o si Every push to the lt NOISE gt button toggles between the two functions NOISE and N REL MAGTEN m To define the reference noise level apply NGISI GOSTA MORI the desired signal to the main input channel and press the lt SET REF gt but ton This reference value is shown in the NREL La Auien J bottom display in the generator unit e A EJ Now apply the signal to be measured to ie A the analyzer The displayed result re flects the ratio of the input noise level to fe J the stored reference Keep in mind that the reference value remains active even after switching Off the system Furthermore please notice that the reference noise level does not equal the reference levels of other relative measurement functions e g L
109. tion product The high frequency signal component f2 can be set to any frequency above 4kHz This al lows also to perform IMD sweeps The 4kHz limit avoids that intermodulation products are filtered out by the highpass filter i e that possible harmonics of the low frequency tone would not to be measured a AAR To select the IMD function press the ae aie lt IMD gt button which is identical to the es lt THD N gt key until the LCD shows MD NPEL uvi IHIN Each further press toggles between the N THD N and IMD measurement functions MEER Al wD w pipera 52 104 Eii Eii V3 1 A2 Audio Test amp Measurement System User Manual Activation of the IMD measurement function will automatically make the actual IMD test signal the output signal of the A2 A2 D This is indicated by the illuminated ALT LED on top of the lt GEN SIGNAL gt button The type of the IMD test signal is displayed in the generator status line on top of the METER display see chapter Standards below The frequency range of the higher frequency is limited from 4kHz to 40kHz The displayed generator frequency represents the frequency of the higher tone while the lower tone is fixed to either 60Hz or 250Hz Should the selected generator frequency exceed this range then it is automatically set to the min max allowed IMD frequency The displayed readbck level equals the RMS level of the output signal The displ
110. ts Mute Synchronization Numerical Result 0 Option Overview Phantom Power RS232 Output Frequency Impedance Eii Hii V3 1 A2 Audio Test amp Measurement System Impedance Display Impedance S Level Signals Stage e Transformer Option P PC Interface guises 14 Phantom Power Input Impedances sccciaiverceesscereverserecssccnvee Option on ona Phase Measurement Pin Assignment Centronics Connector seseeseeeseeeeeeeeee 87 RS232 Connector Cable eeeee 87 Pink Noise Level Selective Analysis 00 61 Output Signal Power Mains Printer Connector Driver Error Settings Type Menu Printout eirasid ka METER Display iisi 37 Q QUASEPCAK oinnia as 35 55 R RANGING sieis Readback Reading Monitor Ou tput Real Time Clock Re Calibration Recall amp Store Instrument Setup Sweep Graph Reference Level L REL Measurement 0c ecceeeeeees LEVEL Measurements N REL Measurements NOISE Measurements Re Scaling of Sweep Graph Resolution in Time Sweep Mode Menu of Sweep Result Display RMS User Manual Interface Option Scaling of Sweep Graph X Axis of Sweep Graph Y Axis Scope Display Mode Freeze Display ee Screen SAVE 0 ee eeeeseeeeeeeesereeeseeeneeees Scroll Bar graph Sweep Graph Sensitivity of Bar graph of Swe
111. uently the last recorded trace will be stored perma nently Any new sweep curve will be added to the same graph as long as actual the measurement function is not altered Graphics Toclear the current graph use the command Del Kept This Save to M1 command deletes all kept traces but leaves the actual trace Save to M2 untouched peer ya e If you wish to delete the last not yet kept trace use com Recall M2 mand Del Actual Recall M3 Keep Sweep Keep in mind that a recorded trace can be printed out only if it Dal Kept Dal Actuni as been kept before EXIT Store amp Recall Sweeps The A2 A2 D also offes the possibility to store the actual graph to one of three available memory locations The stored information comprises the measurement function the sweep mode the actual set of kept traces the scaling and the time amp date of the internal real time clock The memory is battery backed up so that the instrument may be disconnected from mains power and moved to another locations to get the printouts etc To store a graph select the menu behind the lt GRAPH gt button and select one of the three Save to Mx entries by using the lt SCALE gt wheel A push on the wheel confirms the selection and stores the Graph Depending on the resolution and the measurement function up to 6 traces can be recorded per graph The minimum capacities are Function Resolution HIGH Prec Ty V3 1 om
112. ut Imp 100kOhm Filter LEVEL Sine Off 1 000 V 1 000kHz A 775 6 mV 1 000kHz 775 6 mV SSS aS SS Sea ennie a a a a aa Fig 14 Example of a METER Display Printout FETI V3 1 om 37 104 User Manual A2 Audio Test amp Measurement System GRAPH Display Mode Apart from the ability to measure and display single results the A2 A2 D offers a big variety of sweeps sweep sequence of measurements plotted vs the variation of one parameter as well The GRAPH display mode supports best the definition of the sweep setup and al lows to show the recorded curves The available sweep modes of the A2 A2 D are e Internally controlled frequency sweeps e Externally controlled frequency sweeps e Amplitude sweeps e Time sweeps e Table sweeps Fig 15 GRAPH Display Example The A2 A2 D2 comprises an curve tracer feature that automatically controls and displays the selected sweep type It is able to record up to 6 sweep curves in one graph depending on the resolution thus allowing their comparison Furthermore 4 complete graphs may be stored in the internal memory of the A2 A2 D They remein stored even after power Off and can be recalled at any time to be printed out or for additional sweep curve recordings The running and the fixed generator parameters are displayed on top of the GRAPH display together with the selected measurement function The scaling of the Y axis may be done either manually or aut
113. ution Pippe V3 1 oe 69 104 User Manual A2 Audio Test amp Measurement System RES Min Max LOW 2 50 HIGH 30 200 Performing a Sweep As soon as the sweep parameter definition has been finished the only step remaining is to start the sweep by pressing the lt DO SWEEP gt gt lt STOP gt button DA SWEET Ar LIN Baal ale EWER MED IE S N S NA Ton CW l XT Os A O GO GO CG Ta This button starts a new or stops a running sweep Keep in mind that a running sweep will be processed and scaled automatically NOTE Ifthe sweep doesn t start after the DO SWEEP command then the sweep mode is most probably set to external Synchronization Internal External Normally the variable sweep parameter e g frequency is controlled internally by the gen erator of the A2 A2 D so that the analyzer may be synchronized automatically to this pa rameter Nevertheless there are also applications where the variable sweep parameter is generated externally so that the analyzer of the A2 A2 D must synchronize itself to this parameter Unfortunately this cannot be done for all of the three available sweep parameters For in stance synchronization to the externally generated swept amplitude of an amplitude sweep is not possible In practice the synchronization of the A2 A2 D analyzer is necessary for THD N Level Se lective and Crosstalk measurements Each of these fu
114. weep setup SET REF To memorize a special setup as well as to recall this stored or to recall the factory settings open the A2 Setup menu by cS double clicking the lt SET REF gt key AZ Setup powe the arrow to the selection Store Setup and confirm by Store Setup turning and pushing the lt SCALE gt wheel There is only one Recall Setu location available for a user defined setup Recall Default gt gt Interface Calibrate A2 Leave the menu without a change through the entry EX T or gt Set Clock by any other keypress gt AutoDetect EXIT NOTE Keep in mind that if the default setup is recalled the current settings are lost unless they have been saved before Calibration The A2 A2 D has been designed to require almost no maintenance Actually the A2 A2 D is able to re calibrate itself automatically by measuring the parameters of each internal amplifier filter and rectifier These parameters are stored in a table and used for calculation of the measurement results This re calibration procedure may be processed if the A2 A2 D is used in extreme environments as e g with very high low temperatures or humidity Re calibration of the A2 A2 D should be carried out by qualified personnel only Contact your NTI agent if in doubt To start the re calibration procedure proceed as follows aa eae ae V3 1 om 85 104 User Manual A2 Audio Test amp Measurement System 1 Warm up t
115. wept at all NOTE Several sweeps can be recorded re scaled and printed in the same graph and up to four complete graphs can be stored in the internal memory of the A2 A2 D for later use and printout Preparing a Sweep Sweeps are normally visualized in the GRAPH display mode that can be entered any time by pressing the lt GRAPH gt button Keep in mind that even during the preparation or execu tion of a sweep all three display modes METER GRAPH and SCOPE may be entered To prepare a sweep first define the sweep limits i e the start stop values Although the A2 A2 D offers default settings they can be adapted individually to the actual demands Next the resolution i e the number of measurement points between these limits has to be set Last but not least select the measurement function to be recorded After starting the sweep the A2 A2 D takes over control of the entire process including ranging and display scaling It automatically chooses internal settling parameters to make the sweep as fast but as accurate as possible too Almosr simultaneously the recorded curve becomes visible in the GRAPH display If necessary the recorded curve can be kept in the internal memory of the A2 A2 D together with the following one etc In this way up to six traces may be stored in one graph Of course the complete analysis of a DUT may consist of several graphs acquired with dif ferent measurement functions Therefore f
116. y pressing the lt UNIT gt button on the right hand side of the front panel FETTI V3 1 om 35 104 User Manual A2 Audio Test amp Measurement System FATER Each keypress steps to the next avail wi uwin Lian 23 aN NI able unit 7 If there are no alternative units e g C CT fe J N with measurement function W amp F pre ceren is sing the unit button has no effect Aon a STIP SWEEP MIZE VA UE NT EXT h NOTE The lt UNIT gt button influences the unit of the measurement result only i e not the generator level unit except of measurement functions LEVEL and 2 Channel where the units are coupled together The Bar graph The bar graph displays the measurement result in an analog way This makes the bar graph very helpful to identify trends and tendencies of changin g unstable signals or when doing adjustments to minimize maximize a signal Normally in the AUTO mode the bar graph is scaling automatically but its scale can be zoomed and scrolled to any point in the measuring scale manually Zooming the Bar graph Scale The lt SCALE gt softwheel provides the possibility to adjust the bar graph scale exactly to your needs To enter the ZOOM mode push the lt SCALE gt wheel once Each further push to the lt SCALE gt wheel will toggle between ZOOM and SCROLL mode To return to the AUTO mode double click on the wheel e In the ZOOM mode every CW incremental step of the
117. y shift if using this mode Filter control externally i e by the dominant frequency of the input signal may be useful and necessary if the DUT is stimulated by another signal source than the A2 A2 D generator e g a test tape To set the control of the filter center PaT AA ee MODE CEN ICNAL frequency to either mode use the lt INT EXT gt button Each press tog a gles between the two settings e INT means that the notch filter is locked to the generator frequency i e EXT will synchronize the notch i PUSH filter to the dominant input fre _ quency Hint The status of the lt INT EXT gt key only has an effect for measurement functions with variable filters such as THD N L SEL and X TALK v LEVEL Additional Filters The A2 A2 D allows to additionally use the complete set of availabel filters for THD N meas urements If no additional filter is activated the bandwidth is limited to 250kHz Activating the Audio bandpass filter 22Hz 22kHz primarily reduces the noise content of the signal But be careful it will also reject all harmonics above 22kHz For instance with a stimulus of 6kHz and activated Audio bandpass filter the THD N result would make no sense since already kg the 3 harmonic and all upper harmonics will not be considered The 400Hz highpass filter mainly eliminates low frequency disturbing signals like hum and its harmonics as well as rumble However do notmeasu
118. z true RMS 10Hz 100kHz 10mV 200V lt 18dB 1 20H240kHz DIN 45403 SMPTE and TH 22 51 1 1 4 1 10 1 60Hz 250Hz 4kHz 40kHz sweepable V3 1 tae oe Lis i 97 104 User Manual A2 Audio Test amp Measurement System Residual IMD lt 90dB U gt OdBV 1 1 4kHz Crosstalk Level Selective Range 10Hz 50kHz Accuracy 0 3dB Filter tracking 2 pole BP Q 5 Rectifier true RMS Residual Noise lt 0 7 uV lt 123dBV Ref 1kHz DIN audio BP Noise Filter Weighted CCIR 468 3 Filter Unweighted DIN audio bandpass 22 4Hz 22 4kHz Rectifier quasi peak according CCIR 468 3 Residual Noise lt 104dB weighted quasi peak lt 108dB unweighted quasipeak lt 116dB weighted RMS Wow amp Flutter Function Standards IEC 386 DIN 45507 CCIR 409 BS 4047 1972 quasi peak NAB JIB C 5551 RMS Range 0 1 10 full scale Accuracy 3 of reading Frequency 3kHz or 3 15 kHz Input Voltage 100mV 100V Drift Range 15 Accuracy 20ppm 0 002 Frequency Function Display Mode Continuous Frequency Range 10Hz 200kHz Resolution min 0 1 Accuracy 0 05 Scope Function Trigger Mode Auto Scaling Auto 100uV 20V Div Time Base Auto 10 us 20ms Div Sampling Rate max 2MS s 98 104 HEE v3 1 A2 Audio Test amp Measurement System User Manual Filters 400Hz Highpass 10 3 pole Bandpass 22 4Hz 22 4kHz DIN 10 3 pole Noise Filter CCIR 468 4 Selective Filter 2

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