Universal Audio 1176LN User Manual Download Page 26 | Manualshive

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The Technical Stuff
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26

“Q” Bias

The compression threshold is set using R59. Under normal circumstances, this control does not need
to be adjusted. The threshold is dependent upon the specific characteristics of the VVR FET (Q1), and
it will be necessary to re-adjust it if Q1 is changed.

The following procedure is used to set “Q” bias:

1.

Select 4 or +8 output metering.

2.

Adjust R59 fully counterclockwise (CCW).

3.

Apply a sine wave signal to the 1176LN.

4.

Adjust the Input and Output controls for 0dB output.

5.

Slowly adjust R59 CW until the output decreases by 1.0 dB.

Meter Driver Null

A multimeter is needed to perform this calibration procedure:

1.

Disconnect any input and output connections on the 1176LN.

2.

Set your multimeter to measure DC volts.

3.

Depress the Meter GR pushbutton.

4.

Adjust the Zero potentiometer R71

(



see page 25)

so that the meter reads near 0 dB.

5.

Connect the multimeter across R74.

6.

Adjust R75 for a minimum voltage reading.

7.

Disconnect the multimeter.

8.

Readjust the Zero Set potentiometer R71 so that the meter reads 0 dB

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Summary of Contents for 1176LN

Page 1: ...Model 1176LN Solid State Limiting Amplifier Universal Audio Part Number 65 00046 Universal Audio Inc Customer Service Tech Support 1 877 MY UAUDIO Business Sales Marketing 1 866 UAD 1176 www uaudio com ...

Page 2: ...ciated software artwork product designs and design concepts are subject to copyright protection No part of this document may be reproduced in any form without prior written permission of Universal Audio Inc Trademarks Universal Audio the Universal Audio diamond logo UAD UAD Series UAD 1 UAD 2 UAD 2 SOLO UAD 2 DUO UAD 2 QUAD Powered Plug Ins 1176LN 1176SE Teletronix LA 2A LA 3A LA 610 LA 610MkII 2 ...

Page 3: ...ransformer input stage LN circuitry and a Class A 1108 style output stage Later versions replaced the Class A output stage with a push pull Class AB output stage and eventually replaced the transformer input with a differential op amp circuit but most engineers agree that the D E versions best represented the vintage sound that has become treasured the world over Most of us at Universal Audio are ...

Page 4: ... the plug body when connecting or disconnecting it 7 Grounding of the Plug This unit is equipped with a 3 wire grounding type plug a plug having a third grounding pin This plug will only fit into a grounding type power outlet This is a safety feature If you are unable to insert the plug into the outlet contact your electrician to replace your obsolete outlet Do not defeat the purpose of the ground...

Page 5: ...l Button Mode About Class A Making A Custom Insert Cable Terminal Strip Connections Maintenance Information Calibrations Zero Set Q Bias Meter Driver Null Stereo Operation and Calibration Changing the Voltage Selector Changing Fuses 1176LN Circuit Details Glossary of Terms Recall Sheet Specifications Additional Resources Product Registration Warranty Service Support 3 4 6 8 11 12 13 17 17 19 22 22...

Page 6: ... place it there The 1176LN is housed in a standard two rackspace 19 chassis and so we recommend that it be securely mounted in a rack if possible Step 2 On the rear panel make sure the voltage selector switch is set correctly for the voltage in your area On the right side of the front panel make sure the bottom Meter button OFF is pressed in and then connect the supplied IEC power cable to the rea...

Page 7: ...sion ratio of 1 1 thus adding color but with no gain reduction Depress the 4 Ratio button 4 1 and slowly raise the Attack knob to hear the effect of moderate compression on your signal Step 9 Experiment by selecting different Ratios and by trying All Button mode pressing in all four Ratio buttons simultaneously Also try varying the Input level and Attack and Release times for different compression...

Page 8: ...e amount of time it takes the 1176LN to return to its initial pre gain reduction level The 1176LN release time is adjustable from 50 milliseconds to 1100 milliseconds 1 1 seconds The release time is fastest when the Release knob is in its fully clockwise position and is slowest when it is in its fully counterclockwise position If the release time is too fast pumping and breathing artifacts can occ...

Page 9: ...atio moderate compression 8 Selects an 8 1 ratio severe compression 12 Selects a 12 1 ratio mild limiting 20 Selects a 20 1 ratio hard limiting Unlike many other devices the 1176LN Attack and Release times get faster not slower as their corresponding knobs are turned up clockwise Pressing all four Ratio buttons in simultaneously yields an extreme form of compression that many engineers love When t...

Page 10: ... to a level of 4 dBm at the rear panel outputs see 2 and 4 on the following page Depressing the OFF position has the effect of powering off the 1176LN In order to obtain a specific amount of limiting or compression on the 1176LN begin by setting both the Input and Output knob to approximately 24 their twelve o clock positions for unity gain Set the Ratio as desired then set the Attack and Release ...

Page 11: ...ally be arriving via a patchbay from a channel or bus insert send 4 Terminal Strip Because it predated standard XLR connectors the original 1176LN provided terminal strips for input and output line level connections and so in addition to providing a convenient XLR input and output see 2 and 3 above that feature has been retained here Use the leftmost two terminals for input connections the next te...

Page 12: ...____________________________________________ 12 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1176 SA For most applications we recommend starting with the 1176LN INPUT and OUTPUT knobs set to approximately 24 their 12 o clock position for unity gain ...

Page 13: ...but I can t be without at least a pair of 1176s and an LA 2A The 1176 absolutely adds a bright character to a sound and you can set the attack so it s got a nice bite to it I usually use them on 4 1 ratio with quite a lot of gain reduction I like how variable the attack and release is there s a sound on the attack and release which I don t think you can get with any other compressor I listen for h...

Page 14: ...ique What you do is you run your room mics through a couple of 1176s just so that they are nudging a bit This brings up the decay time of the room when your guy hits the bass drum or the snare If it s a very quick tempo it won t work but at medium or half time tempo it brings up the room It s wonderful and there is not another compressor that will do it the same way as an 1176 When I am mixing he ...

Page 15: ...e controls and with careful positioning it was possible to give the guitar a lot of punch and an apparent sense of urgency in the mix The 1176LN can serve as a perfect complement for acoustic and electric bass as well In his Sound on Sound magazine review in June 2001 Hugh Robjohns observed that the original 1176 was often celebrated as a compressor for bass and I certainly found the re issue s co...

Page 16: ...helps tracks to cut through in a mix without you needing to even reach for EQ Throughout the years engineers have variously referred to this characteristic sound as edge growl present and urgent Generally speaking the higher the Input level the more these descriptive terms come into play You ll find that the 1176LN is most transparent when doing gain reduction of 4 dB or less This will serve to su...

Page 17: ...ous configurations and eventually found a way of using it as the gain controlling element of a compressor limiter The original version of the 1176 released in 1967 was denoted the 1176A but was revised to the model AB only a few months later with improvements in stability and slightly reduced noise The following year saw revision B with further minor changes to the preamplifier circuit These model...

Page 18: ...re launched Universal Audio In 2000 the company released its first product a faithful reissue of the original 1176LN revision D E which quickly garnered rave reviews finding a home in hundreds of professional and project studios worldwide In 2000 Bill Putnam Sr was awarded a Technical Grammy for his multiple contributions to the recording industry Highly regarded as a recording engineer studio des...

Page 19: ...t peak levels causing distortion While many of today s digital recording media approach or even exceed 120 dB of available dynamic range quiet passages of recorded music can still be lost in the ambient noise floor of the listening area which in an average home is 35 to 45 dB Despite the increased dynamic range compression is especially important when recording digitally for two reasons One it hel...

Page 20: ...ibes the amount of increase required in the incoming signal in order to cause a 1 dB increase in output A ratio of 1 1 therefore means that for every 1 dB of increase in input level there is a corresponding 1 dB increase in output level in other words there is no compression being applied A ratio of 4 1 however means that any time there is an increase of 4 decibels in the loudness of the input sig...

Page 21: ... in its attack and release times these are the parameters which most affect how tight or how open the sound will be after gain reduction The attack time describes the amount of time it takes the limiter compressor circuitry to react to and reduce the gain of the incoming signal usually given in thousandths of a second milliseconds or even millionths of a second microseconds A fast attack kicks in ...

Page 22: ... the attack of initial transients a phenomenon which might be described as a reverse look ahead The ratio goes to somewhere between 12 1 and 20 1 and the bias points change all over the circuit thus changing the attack and release times as well The unique and constantly shifting compression curve that results yields a trademark overdriven tone that can only be found in this family of limiter compr...

Page 23: ...pins 1 cold and 3 ground together on each XLR connector Only solder pin 3 as you will also need to solder an audio lead into pin 1 2 On both XLR connectors solder the hot white lead into pin 2 and solder the cold black lead into pin 1 as well as the other end of the bus wire as described in the previous step 3 Solder the hot white lead from the cable connected to the male XLR to the tip connection...

Page 24: ...e lead TS tip to the IN terminal Connect the GROUND shield braid to the IN C terminal UNBALANCED OUTPUT Connect the HOT cable lead TS tip to the OUT terminal Connect the GROUND shield braid to the OUT C terminal BALANCED INPUT Connect the HOT cable lead TRS tip or XLR pin 2 to the IN terminal Connect the NEUTRAL cable lead TRS ring or XLR pin 3 to the IN C terminal Optional If there is a hum probl...

Page 25: ... 1176LN 2 Depress the Meter GR pushbutton 3 Set the Input control fully off turn the knob fully counterclockwise 4 Use a small screwdriver to slowly adjust the Zero Set potentiometer so that the meter reads 0 dB Watch how the meter settles before completing the calibration There are no user serviceable parts inside the 1176LN Unit calibration as well as repair should only be performed only by qual...

Page 26: ...unterclockwise CCW 3 Apply a sine wave signal to the 1176LN 4 Adjust the Input and Output controls for 0dB output 5 Slowly adjust R59 CW until the output decreases by 1 0 dB Meter Driver Null A multimeter is needed to perform this calibration procedure 1 Disconnect any input and output connections on the 1176LN 2 Set your multimeter to measure DC volts 3 Depress the Meter GR pushbutton 4 Adjust th...

Page 27: ...th ends connect the 1176 SA to both 1176LNs 4 Depress the Meter GR pushbutton 5 Adjust the potentiometer on the 1176 SA until both meters read 0dB If it is not possible to zero both meters reverse the stereo interconnect cables and repeat the preceding step When used in stereo operation the Attack and Release controls on the two 1176LNs will interact so that changing the Attack or Release times on...

Page 28: ...sired operating voltage NOTE When changing operating voltage the fuse value must be changed as well Make sure the 1176LN is properly set for the voltage in your area before applying AC power to the unit Failure to do so may damage the unit Changing Fuses The AC power fuse is located in the AC power connector block Remove the power cord before checking or changing the fuse A 125 mA time delay slow ...

Page 29: ... and performance is critical to the sound of the device This transformer was distinguished by the fact that it used several additional sets of windings to provide feedback a practice widely used in the tube amplifiers of the era which made it an integral component in the operation of the output amplifier Putnam spent a great deal of time perfecting the design of this tricky transformer and careful...

Page 30: ...lowed by a transformer The purpose of this section is to reduce the signal level so as not to overdrive the FET based gain reduction stage Additionally the adjustable input level is used to control the amount of compression This input circuit was used in Revisions A F With Revision G a differential op amp input instead of the attenuator transformer input stage was used Gain Reduction Stage Figure ...

Page 31: ...lower the gain hence reducing the signal level This is the basis of the limiting action Note that the 1176LN is a feedback style compressor since the sidechain circuit samples the signal level after the gain reduction LN Circuitry The LN circuit which appeared in revisions C and later was designed to reduce the distortion that the FET introduced in the gain reduction stage FETs are inherently nonl...

Page 32: ...m transformer designed by Bill Putnam Sr Aside from offering output impedance matching the transformer forms an integral part of the feedback network used to stabilize the output stage Note that later revisions F and beyond used a push pull class AB output stage Revision E was essentially the same as revision D Revision E added 220 Volt operation as well as a 10 MΩ resistor across the ratio switch...

Page 33: ...s is then fed to CR2 Note that the signal applied to CR2 is 180 out of phase with the signal at CR3 Since they are out of phase the combination of CR2 and CR3 act as a full wave rectifier The output of the rectifiers are then filtered by C22 which smooths the signal This DC voltage is proportional to the level of the input signal A bias level is applied to the diodes by the Compression Ratio pushb...

Page 34: ...lectronic devices such that their active components are drawing current and working throughout the full signal cycle thus yielding a more linear response This increased linearity results in fewer harmonics generated hence lower distortion in the output signal Clipping A particularly harsh form of audio distortion caused when the loudness of an incoming signal exceeds a digital audio recording devi...

Page 35: ...ether the device will reach maximum gain reduction quickly or slowly A gradual transition is called soft knee while a more rapid transition is called hard knee Soft knee compression and limiting is generally more desirable for musical applications Limiter A compressor that operates at high compression ratios of 10 1 or higher Limiting A more severe form of compression where a high compression rati...

Page 36: ...An electronic component consisting of two or more coils of wire wound on a common core of magnetically permeable material Audio transformers operate on audible signal and are designed to step voltages up and down and to send signal between microphones and line level devices such as mixing consoles recorders and DAWs Transient A relatively high volume pitchless sound impulse of extremely brief dura...

Page 37: ...eet _______________________________________________________________________ 37 Universal Audio Inc 1700 Green Hills Rd Scotts Valley CA 95066 4926 www uaudio com 877 MY UAUDIO voice 831 440 1176 fax 831 461 1550 ...

Page 38: ... to Noise Ratio 81 dB with input signal at threshold of limiting over a bandwidth of 30 Hz to 18 kHz Attack Time Adjustable from 20 to 800 microseconds Release Time Adjustable from 50 milliseconds to 1 1 seconds External Connections XLR Original Jones barrier strip Stereo Interconnection Optional using 1176SA stereo interconnect accessory Power Requirements 115V 230V Power Connector Detachable IEC...

Page 39: ...our goal here at UA is to get you up and running again as soon as possible The first thing to do if you re having trouble with your device is to check for any loose or faulty external cables bad patchbay connections grounding trouble from a power strip and all inputs outputs mic line Hi Z etc If your problem persists call tech support at 877 MY UAUDIO or send an email to hardwaresupport uaudio com...

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