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M80 User Guide_4 - Studio Technologies, Inc.
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1. 80 User Guide Studio Technologies Inc low pass filter is connected to inputs on three sections of integrated circuit com parator Four precision resistors are con nected in series with the 15Vdc power supply rail to create three DC voltages These act as reference voltages and are used as the switching points for the com parators The outputs of two of the com parator sections are connected as an OR gate and control the Lo LED The third comparator section controls the Hi LED Notice that the comparators are con nected such that the LEDs light simulta neously only over a very small voltage range This is the calibration window that the user observes The current through the LEDs is directly controlled by transistors whose bases are driven by pull up resis tors on the outputs of the comparators ExactCal One of the highlights or should we say hype lights of the Model 80 is the ExactCal section To a user the ExactCal controls and LEDs allow a wide range of input signals to be precisely interfaced with the Model 80 ExactCal is a term that Studio Technologies selected to describe the combination of the audio input and metering circuitry The audio input circuitry allows a user to adjust the input sensitivity to match the level of the audio source The metering circuitry provides the user with visual feedback allowing the controls to be set to the correct position Audio Outputs Eight identical circuits provide
2. Selection Each of the eight stereo line level outputs is individually configurable for a 10 or 4dBu nominal output level Eight DIP type switches located on the right side of the front panel are used to set the output levels The legend on the switches corre spond to the output channel numbers A switch that is set to the up position sets its associated output channel for 10dBu A switch set to the down position sets the output for 4dBu A small screw driver may be of assistance when setting the switches Operation Now that you ve installed and configured the system you re ready to go You should find operation very easy as there is almost nothing to do on a day to day basis For peace of mind the ExactCal LEDs will give you a visual indication whenever audio signals are present on the Model 80 s input The LED labeled Lo will light whenever the input signal is within the range of 18dB below and 0 5dB above the nominal oper ating level The LED labeled Hi will light Issue 4 March 1997 Page 12 any time the input signal is greater than 0 5dB below the nominal operating level This sounds a bit confusing but isn t really so hard to understand As an example if you have a nominal 4 signal con nected to the Model 80 s line input and the ExactCal section has been used to calibrate the input the Lo LED will light when the signal is between 14 and 4 5dBu the Hi LED will light when the signal e
3. the eight stereo line level outputs Each of the eight Circuits is essentially two identical circuits that share a common nominal output level control lead For simplicity only the left channel of a stereo output circuit will be described Issue 4 March 1997 Page 17 Studio bola The left channel internal audio bus is connected by way of a resistor to the inverting input of an operational amplifier The operational amplifier is configured as an inverting adjustable gain circuit One section of high performance analog switch controls the gain of the op amp by shunt ing a resistor in the feedback loop When the analog switch is in the off open state the op amp is operating at essentially unity gain When the analog switch is in the on closed state the gain is less than unity providing an attenuation of 14dB voltage The state of the analog switch is controlled by one section of DIP switch The DIP switch which produces a 0 or 15Vdc logic signal is accessible to the user by way of the front panel The output of the op amp is capacitor coupled to the input of an SSM 2142 differential balanced line driver inte grated circuits The 2142 provides an electronically balanced low impedance output and is capable of driving high signal levels into 600 ohms or greater Because of the nature of a differential driver an effective 6dB boost in signal level is achieved The outputs of the 2142 are directly connected to the o
4. the front panel The pot adjusts the input sensitivity for both the left and right inputs Note that the coupling capacitors used to couple the 2143s to the pot are a nonpolar type allowing for small DC voltages of unknown polarity to be re ceived on the inputs The wiper of each section of pot is connected to the non inverting input of a section of low noise operational amplifier The voltage gain of the left channel op amp is fixed at approxi mately 15dB The combination of a fixed resistor and trim potentiometer allows the voltage gain of the right channel op amp to be adjustable over a nominal range of 13 to 17dB This implements the right trim function accessible from the front panel allowing differences in the left and right signal levels to be accounted for The output of the left channel op amp section is defined as the left channel internal audio bus Its nominal level is 2dBu The same holds true for the right channel op amp where its output is the right channel inter nal audio bus Metering Outside of the overall system architecture the metering section of the Model 80 is probably the most unique Two identical meter circuits monitor the audio level on the left and right internal audio buses Audio signal enters each meter circuit via an operational amplifier configured as a half wave synchronous rectifier The result ing DC output is smoothed via a resistor capacitor low pass filter The output of the Model
5. the plugs you use must comply with industry standard RS 453 Switchcraft No 297 Neutrik NP3C or equivalent will work correctly Refer to the Technical Notes section for details Audio Input The Model 80 provides one stereo line level input It is electronically balanced and is compatible with balanced or unbal anced signals that have a nominal level range of 10 to 10dBu The ExactCal section allows precise level calibration with the connected input signal It is anticipated that in most cases a stereo signal will be connected to the input The Model 80 can also be used as a 1 input 16 output mon aural distribution amplifier or as a dual 1 input 8 output monaural distribution amplifier Issue 4 March 1997 Page 9 Studio bola Prepare the input plugs so that tip is positive or hot ring is negative or cold and sleeve is shield The input jacks will also accept unbalanced 1 inch 2 conductor phone plugs With unbal anced phone plugs tip is positive or hot and sleeve is shield If 3 conductor phone plugs are used to connect unbal anced signals connect positive or hot to tip and connect shield to ring and sleeve Loop Through The two loop through jacks are electrically wired in parallel with the two input jacks With this arrangement several applications are possible such as allowing the input signals to be routed to another stereo input without the use of Y adapters The source si
6. the standard Why is this relevant to you Because the phone jacks used on the Model 80 do comply with the standard Issue 4 March 1997 Page 14 They expect to be mated with plugs that also meet the specification When interfac ing with the Model 80 be careful with the plugs you utilize Should a connection appear flaky sound noisy or make an intermittent contact the most likely prob lem is anonstandard phone plug Replace the plug if this is the case You should find that all plugs from Switchcraft or Neutrik will work correctly specifically Switchcraft No 297 or Neutrik NP3C Definition of Level dBu Whenever possible Studio Technologies has opted to use the dBu designation as it seems to be quite rational Using dBm was fine when all audio line outputs were terminated with 600 ohm loads In this way it was easy to say that OdBm is 1 milliwatt dissipated in the known load i e 0dBm across 600 ohms will measure 0 7747V In contemporary situations an output is rarely terminated with 600 ohms generally 10k ohms or higher The dBu designation is better because it refers to dB referenced to 0 7747V with no reference to load impedance This takes into account today s audio scene where signals have a low source impedance and a high input impedance The dBu designation is be coming the standard for the professional audio industry 10 Output Level Reference To those of you who are technical nitpickers
7. we feel than an explanation is in order Operational simplicity rather than historical convention led Studio Technologies to make the 10 outputs referenced to dBu rather than to dBV We are well aware that in the past a 10 output was often referenced to 1 volt not to 0 7747 When the Model 80 was first designed it was assumed that the 4 Model 80 User Guide Studio Technologies Inc Studio oola output would be in dBu and the 10 output would be in dBV We soon real ized that this would cause cranium problems for many users A user monitor ing one of the Model 80 s outputs would expect to see a 14dB drop on their VU meter when going from the 4 to the 10 DIP switch position on the Model 80 s front panel They actually would be switching from a 4dBu output to a 10dBV output a difference of 11 78dB confusion would immediately reign To avoid this situation we took the liberty of keeping the 10 referenced to dBu This should in no way effect the ability of the Model 80 to inter face with other equipment while making life easier for everyone Circuit Description This information will help you under stand how the Model 80 functions and if required help you identify where a failure may be located Please refer to the attached block and schematic diagrams while reading this material Schematic Nomenclature The schematics show the graphical repre sentation of all the electro
8. 97 Page 13 Studio bola To confirm that a signal is present on the input of the Model 80 you can plug the headphones into the loop through con nectors associated with the left and right channels After ensuring that the level will not hurt your ears you can listen for the presence of audio and get an idea of the general quality of the source With a bal anced input signal you should hear the input in both the left and right earpieces of the headphones With an unbalanced source you would in most cases hear signal in only the left channel of the phones To confirm that signals are present on the eight stereo outputs you can plug the headphones into the left and right output jacks Outputs configured for 4dBu operation will be significantly louder in the headphones Since all Model 80 out puts are balanced you should observe signal in both the left and right earpieces Rapidly walking through the 16 output jacks will confirm the proper operation of the Model 80 Technical Notes Y Inch Plugs versus EIA RS 453 An incompatibility problem lurks between some inch phone plugs and the jacks found on professional audio equipment While all the plugs seem to look the same some do not comply with the indus try standard called EIA RS 453 This standard defines the physical dimensions including the shape of the plug s tip It seems that some plug manufacturers don t bother to make the tip comply with
9. Stuko boka Model 80 Stereo Analog Audio Distribution Amplifier User Guide Issue 4 March 1997 This User Guide is applicable for serial numbers Model 80 M80 00273 and later Copyright 1997 by Studio Technologies Inc all rights reserved 5520 West Touhy Avenue Skokie Illinois 60077 U S A Telephone 847 676 9177 Fax 847 982 0747 www studio tech com 50200 397 Issue 4 Model 80 User Guide Studio Technologies Inc Studio oola Table of Contents POPS UVM P E 5 NroduUCtiO r a ip EE ENa 7 What This User Guide Covers s es 7 System OVESVIOW eecccceeeeceeeenseeeeeeeeeeeeeeeeneeeeeees 7 System Feat feS sasesana eiaa 7 DPS VANE seeiis aiaga 9 Configuration oo facctta de onehadeacaxinsactndacenstinctacuartancssececansas 11 Operationens eae ase ee gues e Ea 12 Troubleshooting socii 12 Technical Notes sc ietesctnnstptccnstntvianarathiyntsintdnictnGioeiuatessattinut 14 CIRCUIT Description srania caniae noa 15 He 8218 1 151211 sarsma e E a 19 Block Diagram Schematic Diagram Not included in PDF Issue 4 March 1997 Page 3 Studiclook Foreword am pleased to present the Model 80 Stereo Analog Audio Distribution Amplifier As both president and owner of Studio Technologies take a very personal approach when de signing products Getting older 38 as of this writing has increased my appreciation of the more subtle things in life be they a part of nature or the nuances contained in a well desi
10. This is important when supplying bipolar loads such as opera tional amplifiers etc Without these diodes the regulators can latch up when mains power is applied or removed When mains power is initially applied one of the sup plies can come up get to its operating voltage sooner than the other This volt age is fed back through the loads the op amps to the output pin of the other regulator that is still coming up to full voltage Upon seeing this unexpected opposite polarity voltage on its output pin the regulator may get very unhappy possibly latching into a nonoperating state drawing lots of current burning up etcetera The protection diodes keep this condition from happening For service assistance several test points are included on the printed circuit board 20V unregulated 15Vdc and circuit common Analog Circuitry The Model 80 takes advantage of an excellent series of audio specific inte Issue 4 March 1997 Page 16 grated circuits from Analog Devices Using these parts saved us from using literally dozens of additional components More importantly performance levels were achieved that would have been difficult if not impossible to obtain with more conventional circuitry These Analog Devices parts have the common prefix of SSM indicating their roots in a company called Solid State Microelectronics for Music purchased by way of Precision Monolithics a few years ago Hats off to the g
11. accessible to allow rapid discon nection of mains power should it prove necessary As soon as mains power is connected the Model 80 s power present LED will light The unit is now ready for years of trusty service Configuration Input Level Calibration With the ExactCal calibration section it s simple to match the nominal level of the input signal with the Model 80 s internal Circuitry Two controls level and right trim along with four LEDs are the ExactCal operator controls The level control is a stereo device adjusting the input sensitiv ity for both the left and right inputs The right trim control allows the input sensitiv ity for the right channel to be adjusted over a 3cB range This allows compensa tion to be made for small differences in the left and right input levels Two LEDs labeled Lo and Hi are associated with each input They are provided as an aid to calibration as well as serving as signal present indicators Model 80 User Guide Studio Technologies Inc The following is a step by step procedure for using the ExactCal section to match an input signal with the Model 80 e Set the level control fully counterclock wise all the way to the left end of the travel Supply a 1kHz sine wave to both the left and right line inputs Set the level of the source to be precisely the nomi nal operating level If for example the output of a console is connected to the input of the Model 80 t
12. ains power Because the Model 80 is intended for continuous operation an AC mains power switch is not included This serves several purposes eliminating the chance of a power switch being accidently turned off increasing the physical isolation between the nasty 50 60Hz fields and the sensitive analog circuitry and eliminating the physi cal space required by a switch The step down transformer has dual 17V secondaries for 120V and 220 240V op eration and dual 20V secondaries for 100V operation The secondaries are connected in series with the series con nection point providing circuit common as well as being strapped to the metal chassis and the ground pin of the power entry connector The transformer s sec ondary is fed to a full wave diode bridge Issue 4 March 1997 Page 15 Studio bola The output of the bridge is filtered with electrolytic capacitors producing unregu lated 20Vdc Two integrated circuit regulators produce the 15Vdc from the unregulated voltages Capacitors on the outputs of the regulators provide stability The 15Vdc is used by the analog cir cuitry The 15Vdc is also used by the meter circuits The 15Vdc is also used by the power present LED Interesting technical note department notice that a diode is connected from the output pin of each regulator to circuit common These serve to keep the 15Vdc rails at worst case one diode drop 0 7V away from ground in the opposite polarity
13. dance 24k ohms Nominal Input Level 10 to 10dBu Input Level Control allows calibration over 10 to 10dBu input range Right Trim Control allows adjustment of right input level over a 3dB range nominal Maximum Input Level 27 dBu balanced 21 dBu unbalanced Common Mode Rejection 90dB DC and 60Hz 85dB 20kHz 60dB 400kHz typical Model 80 User Guide Studio Technologies Inc Audio Outputs Qty 8 stereo separate left and right output connectors Type electronically balanced direct coupled intended to drive loads of 600 ohms or greater can be connected balanced or unbalanced Nominal Output Level 10dBu 245mvV or 4dBu 1 228V each output individually switch configurable Maximum Output Level Balanced 27dBu into 10k ohms 26dBu into 600 ohms Unbalanced 21dBu into 10k ohms 20dBu into 600 ohms Output Impedance 50 ohms Frequency Response 10Hz 70kHz 0 0 5dB down 1dB 110kHz Distortion THD N 0 004 measured at 4dBu input 4dBu output 20Hz 20kHz S N Ratio 91dB 20Hz 20kHz ref 4dBu Crosstalk 75dB 1kHz ref 4dBu LED Indicators Qty 5 Function 1 power present 4 input level calibration Dimensions Overall 19 00 inches wide 48 3cm 1 72 inches high 4 4cm 6 65 inches deep 16 9cm 1 standard rack space Weight 7 0 pounds 3 2kg Specifications and information contained in this User Guide subject to change without notice Issue 4 March 1997 Pa
14. el control calibration LEDs Studio bola Short circuit resistant the rugged output circuits can drive full signal levels into 600 ohm or greater loads The Model 80 s architecture precludes the need for individual output level trim poten tiometers With the input signal calibrated using the ExactCal section the eight stereo outputs use 1 tolerance compo nents to provide precise 10 or 4dBu outputs Audio Performance The Model 80 is the result of exacting Circuit design combined with the latest state of the art components Like all Studio Technologies products the Model 80 has survived tough listening evalua tions by industry professionals These veterans had the ears to guide us in achieving the right performance The outcome is a product that achieves sonic excellence Model 80 Front Panel ExacTCaL Studio oola Design Philosophy Most audio distribution amplifiers contain a level trim adjustment on each output After careful study Studio Technologies concluded that these adjustments con fused and often interfered with the process of getting maximum audio performance After checking with person nel in the field it became clear that what is desired in virtually every distribution amplifier applications are multiple audio outputs all operating at a standard refer ence level By implementing the ExactCal system the Model 80 s internal operating level can be easily calibrated to match the inp
15. enever mains power is con nected the front panel power present LED should light If the LED is not lit confirm that the main power source is active hot and that the connector on the cord is securely mated with the plug on the back panel For safety in the event of a major internal failure or the connection of incorrect AC mains voltage the Model 80 contains a fuse inside the cabinet The fuse will open blow if the failure of an internal compo nent causes excessive current to be drawn from the internal power supply The fuse will also open should 220 240Vac be connected to a Model 80 that is config ured for 100 or 120Vac operation The fuse is intended to be replaced only by a qualified service technician This person will have the training to safely access the guts of the Model 80 and identify where a problem is located Incorrect Output Levels You must correctly set the input level and right trim controls for the eight stereo outputs to receive a precise 10 or 4dBu nominal output level These controls match the level of the audio input signal with the Model 80 s internal circuitry Refer to the Configuration section of this guide for detailed instructions Intermittent Audio Connections Should you experience audio connections Model 80 User Guide Studio Technologies Inc that seem to be flaky or intermittent refer to the Technical Notes section of this guide The 14 inch 3 conductor pho
16. ge 19 LEFT 1 4 3 COND LINE INPUT 10 TO 10dBu RIGHT 1 4 3 COND LEFT 1 4 3 COND LOOP THRU RIGHT 1 4 3 COND DIFFERENTIAL LINE RECEIVER Ha s S 7 a DIFFERENTIAL INPUT BUFFER BUFFER LINE DRIVER LENELI 2 x t 16 OR 21 gt i i i i i i RIGHT TRIM FOI F Hiss Gig INPUT H CALIBRATION Sy METER LO LEFT G Hse INPUT d H CALIBRATION Sy METER Loss RIGHT AC MAINS FACTORY CONFIGURABLE R 100 120 OR 220 240V 50 60Hz OPERATION FUSE 10 eoo OUTPUT LEVEL 4 R LEFT sl 1 4 3 COND LINE OUTPUT 1 10 OR 4dBu t RIGHT b a 1 4 3 COND CIRCUITRY FOR OUTPUTS 2 8 IDENTICAL TO OUTPUT 1 POWER R POWER e SUPPLY 15V J M80B0_B STUDIO TECHNOLOGIES INC MODEL 80 STEREO ANALOG AUDIO LOCATED ON BACK PANEL DISTRIBUTION AMPLIFIER LOCATED ON FRONT PANEL BLOCK DIAGRAM DIP STYLE SWITCH LOCATED ON FRONT PANEL NOMINAL LEVEL IN dBu DRAWING NO DATE PAGE 30472 06 01 94 01 o 01
17. gnals would be connected to the input jacks The loop through jacks would be used to connect the source signals to the next piece of equipment using 14 inch 3 conductor patch cords Another application would be where more than one Model 80 is used to distribute the same input signal Two inch 3 conduc tor patch cords would link the loop through jacks on the first Model 80 to the input jacks on the second Model 80 Yet another application would be where the Model 80 is used as a 1 input 16 output monaural distribution amplifier The monaural input would be connected to the left input jack and a 14 inch 3 conductor patch cord would connect the left loop through jack to the right input jack Audio Outputs The Model 80 contains eight independent stereo line level outputs which are in tended for connection to a variety of ana log audio devices The outputs are Issue 4 March 1997 Page 10 electronically balanced and capable of driving balanced or unbalanced loads of 600 ohm or greater The outputs can be individually configured for a nominal output level of 10 or 4dBu so you can connect to all line level inputs with no hassle Prepare the output plugs so that tip is positive or hot ring is negative or cold and sleeve is shield The output jacks will also accept unbalanced inch 2 conductor phone plugs With unbal anced phone plugs tip is positive or hot and sleeve is shield If a 3 conductor phone p
18. gned piece of electronic equipment Do the technical and operational aspects of a product work together to feel right A Studio Technologies design is ready to go only when am completely satisfied Many fine people worked toward making the Model 80 happen Mitch Budniak ace consulting engineer designed many of the circuits Jim Cunningham contributed to the analog design Carrie Loving provided engineering support Barbara Govednik coordi nated the marketing communications aspects Ben Kamen designed the automatic testing routines Al Lux designed the printed circuit board Jim McGuire designed the graphics Fred Roeck performed the mechanical design Joe Urbanczyk coordinated the safety testing and agency approvals Additional thanks to Timothy Powell of Metro Mobile Recording Glenview Illinois who provided his excellent ears when issues of sonic quality arose His extensive field and studio experience was extremely helpful in keeping me on the audio straight and narrow Please contact me with your questions comments and suggestions can be reached by voice at 847 676 9177 fax at 847 982 0747 or via the Internet www studio tech com Sincerely Gordon K Kapes President Model 80 User Guide Issue 4 March 1997 Studio Technologies Inc Page 5 Introduction The Model 80 Stereo Analog Audio Distribution Amplifier was developed by Studio Technologies as part of its Studio Tools group of audio support
19. he console output should be adjusted so that the meters read OdB or 100 If the output of the console is a 4 type then setting the console s left and right output levels to nominal should find the console output levels to be exactly 4dBu Slowly turn the level control clockwise As you increase the level watch the LEDs associated with the left channel The LED labeled Lo will light first then both LEDs will light then only the LED labeled Hi will light The correct setting is where both LEDs light Careful adjustment is required as the window where both LEDs light is somewhat less than 1dB Observe the LEDs associated with the right channel If they are both lit no adjustment of the right trim control is required If only one is lit adjust the right trim control using a small flat blade screwdriver so that both LEDs light We like the Xcelite R3324 screw driver it has the clear green handle and is commonly used to calibrate audio equipment Issue 4 March 1997 Page 11 Studio bola For practice mess up the settings of the level and right trim controls Again follow the calibration procedure and again get things set up correctly For future reference it may be helpful to mark the correct input level and right trim adjustment points Use a grease pencil or a piece of adhesive tape so as not to damage the front panel Disconnect the 1kHz signal and con nect the normal audio source Output Level
20. lug is used in an unbalanced application connect positive or hot to tip and connect shield to ring and sleeve AC Mains Power The Model 80 is internally configured to operate from either 100 120 or 220 240V 50 60Hz In most cases units shipped to North America are factory selected for 120V operation Units bound for Japan are selected for 100V while our friends down under and in Europe receive units set for 220 240V Before connecting the Model 80 to AC mains power check that it is config ured to match the local mains voltage Look on the back panel adjacent to the power entry connector for the configured voltage s Note that an incorrect configu ration could seriously damage the unit Should it be necessary to change the unit s operating voltage it must be performed only at the factory or by an authorized service technician The Model 80 uses an IEC standard con nector to mate with the AC mains cord The wire colors in the AC mains cord should conform to the internationally recognized CEE color code and must be wired accordingly Model 80 User Guide Studio Technologies Inc Studio oola Connection Wire Color Neutral N Light Blue Line L Brown Protective Earth E Green Yellow Safety Warning The Model 80 does not contain an AC mains disconnect switch As such the mains cord plug serves as the disconnection device Safety consideration requires that the plug and associated outlet be easily
21. ne jacks used on the Model 80 are of very high quality conforming to the industry standard EIA RS 453 Some plugs do not meet this standard specifically in the shape of the tip conductor In rare cases you may have to replace plugs on inter connecting cables to remedy an intercon nection problem Switchcraft No 297 or Neutrik NP3C phone plugs will function correctly Headphones as a Troubleshooting Tool One of the simplest means of checking for the overall presence of a line level audio signal is to listen to the signal using a pair of stereo headphones The signal level and source impedance of contemporary audio output circuitry can easily drive headphones to quite a high sound pressure level Carefully used headphones are a great means of rapidly determining if signal is present on an audio line Note that in a few cases the plugs used by headphone manufacturers do not comply with the EIA 453 specifica tions for inch plugs You may want to designate a pair of headphones for line level testing and attach a plug of known quality We have found that even some very high quality headphones have non standard plugs be warned Warning Safety First Do not plug a pair of headphones into a jack on the Model 80 while the headphone ear pieces are against your ears High sound pressure levels may be present Only after a signal is connected should you slowly put the headphone trans ducers near your ears Issue 4 March 19
22. nic components along with their electrical value and con nections Traditionally a problem with schematics has been the decimal point marking It either disappears due to bad printing or dust dirt or other imperfec tions end up looking like decimal points For clarity Studio Technologies has adopted a more European component marking scheme Upon first review it may seem quite confusing but it can eliminate problems For resistors the designation K for kilo 1000 has been moved to the decimal point position A 4700 ohm resis Model 80 User Guide Studio Technologies Inc tor is shown as 4K7 rather than 4 7K An example for a one percent value a 49900 ohm resistor would be shown as 49K9 For capacitors the letter r is simply substituted for the decimal point marking A 0 47uf capacitor is shown as r47uf Once you are accustomed to this system you may well prefer it Power Supply The Model 80 contains one linear power supply circuit that generates filtered and regulated 15Vdc The circuit uses a step down transformer with the primary side containing two 115V windings This allows it to be configured for nominal AC mains voltages of 100V 120V or 220 240V For 100V and 120V operation the primaries are connected in parallel for 220 240V operation they are connected in series The configuration is performed using jumper straps on the circuit board For safety a fuse is in series with the incoming AC m
23. operation even for on air broadcast applications System Features One Stereo Input The differential input circuitry is compat ible with balanced or unbalanced signals having a nominal level range of 10 to 10dBu Using laser trimmed compo nents the input offers superior common mode signal rejection To achieve optimal audio performance the ExactCal calibra tion section matches the specific input level with the Model 80 s internal gain structure Two controls and four LEDs allow fast precise calibration Unlike other distribution amplifiers the Model 80 ensures that excellent audio performance can be achieved with little or no hassle In addition to separate left and right input connectors two input loop through con nectors are also provided This simple feature can make installation with related equipment much easier The loop through connectors allow the Model 80 s input source to be connected to another Model 80 or to yet another device Eight Stereo Outputs The Model 80 contains eight independent stereo output sections For compatibility with a range of facilities each output section can be separately configured for 10 or 4dBu nominal output level Each output features an electronically balanced circuit capable of driving balanced or unbalanced loads Operating an output in an unbalanced configuration does not cause its nominal output level to change Issue 4 March 1997 Page 7 Power present LED lev
24. products The Model 80 is designed to work in a large variety of applications Specific applications include audio production duplication broadcast and sound rein forcement All Model 80 functions meet or exceed the performance of the most expensive high end audio equipment What This User Guide Covers This User Guide is designed to assist you when installing configuring and using the Model 80 Stereo Analog Audio Distribution Amplifier It also contains detailed service information including block and sche matic diagrams System Overview The Model 80 from Studio Technologies Inc is the first distribution amplifier that meets the needs of the real world The stereo input is intended to connect to virtually any line level audio source The ExactCal input calibration section allows for optimal audio performance over a 10 to 10dBu input level range The eight stereo outputs meet exacting professional standards Capable of driving balanced or unbalanced loads each output can drive 26dBu into 600 ohms Using front panel switches each output can be individually configured for a nominal output level of 10 or 4dBu The front panel controls and LEDs make installation and setup a simple job The AC mains input power is factory config Model 80 User Guide Studio Technologies Inc ured for 100 120 or 220 240V 50 60Hz operation Components and construction standards make the Model 80 suitable for continuous
25. r North America are shipped with an AC mains cord Your dealer or distributor will provide an AC mains cord for non North American destinations Mounting the Model 80 The Model 80 requires one space ina standard 19 inch 48 3cm equipment rack It is desirable to locate the Model 80 to allow easy access to both the front and the back panels The back panel contains the input and output connectors The front panel is used to access the calibration controls and output level switches The front panel also contains several LED indicators The Model 80 is secured to the equipment rack using two mounting screws per side Audio Inputs and Outputs The Model 80 s audio input and output connections are made using inch 3 conductor phone jacks The choice of phone jacks was simply a matter of real estate 20 XLR connectors don t quite fit on the back of a one rack space unit Don t be concerned about damage to your audio quality the jacks used in the Model 80 are manufactured by Neutrik of Switzerland and feature gold plated contacts for excellent performance Model 80 User Guide Studio Technologies Inc Balanced Connection Input amp Output Ring Sleeve Shield Switchcraft No 297 Neutrik NP3C or equivalent Unbalanced Connection Input amp Output gt ro all Sleeve Shield Switchcraft No 280 Neutrik NP2C or equivalent Caution For reliable audio interconnec tion
26. ut signal Once this input level match ing is accomplished the eight stereo outputs can be individually configured for a 10 or 4dBu nominal operating level In conclusion output trim pots are not included on the Model 80 for the simple reason that better audio performance can be achieved without them MODEL 80 STEREO ANALOG AUDIO DISTRIBUTION AMPLIFIER aanSTUDIO___ TECHNOLOGIES e SKOKIE ILLINOIS U S A Input level Right input trim control Input Model 80 Back Panel 10 or 4 output level configuration switches AC MAINS INPUT Ase INSTRUCTION MANUAL E m L MODEL 80 ore enw Ct00v CAUTION ALL INPUTS AND OUTPUTS oan ov TO PREVENT ELECTRICAL ELECTRICALLY BALANCED e e o2a Dzoav CG geeen hee NEAENCED OPERATION p R STUDIO TECHNOLOGIES INC 50 60Hz PARTS INSIDE REFER SERVICING y SEE INSTRUCTION MANUAL www studio tech com MADE IN USA LOOP THRU INPUT AC mains Stereo line level Loop through Stereo line level connection outputs output input Issue 4 March 1997 Model 80 User Guide Page 8 Studio Technologies Inc Studiclook Installation In this section you will be installing the Model 80 in an equipment rack Audio input and output connections will be made using the Model 80 s multitude of phone jacks AC mains power will be connected to the Model 80 System Components The shipping carton contains a Model 80 User Guide and warranty card Units destined fo
27. utput jack The nominal output level is controlled by our friend the analog switch When the switch is in the off open state a signal at nominal 2dBu is presented to the line driver With the intrinsic 6dB of gain the nominal level at the output jack is 4dBu When the analog switch is in the on closed state a signal at nominal 16dBu is presented to the line driver This results in a 10dBu signal at the output jack Issue 4 March 1997 Model 80 User Guide Page 18 Studio Technologies Inc Studio oola Specifications Model 80 Stereo Analog Audio Distribution Amplifier Mounting One space in a standard 19 inch 48 3cm rack AC Mains Requirement 100 120 or 220 240V 10 factory configured 50 60Hz 100 120V 0 4A maximum 220 240V 0 2A maximum Fusing Qty 1 Type 5 x 20mm time lag Littelfuse 218 series or equivalent Rating 0 400A for 100 and 120V mains power 0 200A for 220 240V mains power Connectors Audio dual 14 inch 3 conductor phone jacks gold plated contacts Manufactured by Neutrik Mates with all plugs specified by EIA RS 453 AC Mains standard 3 blade plug meets IEC 320 specifications Audio Input Qty 1 stereo Separate left and right input connectors Loop Through hardwired in parallel with input separate left and right loop through connectors Type electronically balanced direct coupled Input Compatibility can be connected to bal anced or unbalanced signals Impe
28. uys and gals at Analog Devices Audio Input The Model 80 contains one stereo line level input circuit The input is compatible with balanced or unbalanced signals having a nominal level range of 10 to 10dBu with relative differences in signal level of up to 3cB The function of the input circuitry is to receive the left and right audio signals separate out common mode hum and noise unbalance the signals and process them such that both the left and right signals are presented to the Model 80 s internal audio buses at precisely 2dBu Left and right line level audio enters the Model 80 by way of two inch 3 conductor phone jacks The loop through feature is implemented by simply connecting the left input left loop through and right input right loop through jacks electrically in parallel From the input jacks the audio is also directly coupled into two SSM 2143 differential balanced line receiver integrated circuits The 2143s have excellent common mode rejection low noise and high slew rate Intended for professional audio applications they contain two 12k ohm input resistors individually laser trimmed for accuracy By Model 80 User Guide Studio Technologies Inc Studiclook design the 2143 provides 6cB voltage of attenuation The output of each SSM 2143 is capacitive coupled into one section of a dual stereo log taper potentiometer pot This pot is the input level control that is accessible from
29. xceeds 3 5dBu In most cases the input level control shouldn t be changed as it will change the input calibration In special applica tions you may want to use it as a fader simultaneously adjusting the level on all eight stereo outputs In the fully counter clockwise position the eight outputs are completely off Before you use the level control as a fader ensure that you mark the position of the knob where the input is calibrated If you change the input source you can use the ExactCal section to recalibrate the input Refer to the configuration section of this guide for details Each of the eight outputs are fully inde pendent You can patch reconnect or even short out an interconnecting cable without effecting the other outputs Using the front panel DIP switches you can change the output level of any or all of the outputs whenever you wish Troubleshooting If you re having problems getting the Model 80 up and running this section can help If you haven t read the other sections of this guide you should do so before proceeding Model 80 User Guide Studio Technologies Inc Studiclook If the Model 80 Doesn t Work At All A source of AC mains power must be connected to the Model 80 Depending on the version you have purchased 100 120 or 220 240Vac 50 60Hz is required Con firm what mains voltage is required by observing the selection boxes to the left of the AC mains connector on the back panel Wh
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