Universal Audio 1176LN User Manual

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

Notice
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This manual provides general information, preparation for use, installation and operating instructions
for the Universal Audio 1176LN.

The information contained in this manual is subject to change without notice. Universal Audio, Inc.
makes no warranties of any kind with regard to this manual, including, but not limited to, the implied
warranties of merchantability and fitness for a particular purpose. Universal Audio, Inc. shall not be
liable for errors contained herein or direct, indirect, special, incidental, or consequential damages in
connection with the furnishing, performance, or use of this material.

Copyright

© 2009 Universal Audio, Inc. All rights reserved.

This manual and any associated 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, LA­610MkII, 2-1176, 2-610, 6176, 710 Twin-Finity, 2192, 4110, 8110, SOLO/610, SOLO/110, DCS Remote
Preamp, Cambridge EQ, DreamVerb, Plate 140, Precision Limiter, RealVerb Pro, Precision Buss
Compressor, Precision De-Esser, Precision Maximizer and "Analog Ears | Digital Minds," are
trademarks or registered trademarks of Universal Audio, Inc.. Other company and product names
mentioned herein are trademarks of their respective owners.

Contents of This Box

This package should contain:

• One 1176LN Solid-State Limiting Amplifier

• 1176LN Operating Instructions

• IEC Power Cable

• Registration Card

A Letter From Bill Putnam, Jr.

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Thank you for purchasing the 1176LN Solid-State Limiting Amplifier.

My father designed the original 1176 back in 1966, and he was very pleased with his accomplishment.
He was also very gratified by its reception by his peers in both the recording and broadcast industries.
As a recording engineer, the 1176 was a device he himself used extensively. In making our version of
this legendary piece of gear, we have taken great care to manufacture a compressor/limiter that my
father would have been proud of. Throughout the development of this product, our philosophy has
remained clear: Stay true to the original. There are good reasons why certain pieces of gear have
become classics, and we wanted to make sure that we captured the feel and sound of the original
1176LN accurately.

There were actually many versions of the 1176 produced throughout the years. This reissue is
patterned on the highly recognizable blackface sound of the D/E versions, which were characterized by
the transformer 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 musicians and/or recording engineers. We love the recording process,
and we really get inspired when tracks are beautifully recorded. Our design goal for the 1176LN was to
build a compressor/limiter that we would be delighted to use ourselves—one that induce that “a-ha”
feeling you get when hearing music recorded in its most natural, inspired form.

Developing the 1176LN —as well as Universal Audio’s entire line of quality audio products designed to
meet the needs of the modern recording studio while retaining the character of classic vintage
equipment—has been a very special experience for me and for all who have been involved. While, on
the surface, the rebuilding of UA has been a business endeavor, it's really been so much more than
that: in equal parts a sentimental and technical adventure.

We thank you, and we thank my father, Bill Putnam.

Sincerely,

Bill Putnam, Jr.

Important Safety Instructions
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Before using this unit, be sure to carefully read the applicable items of these operating instructions and the
safety suggestions. Afterwards, keep them handy for future reference. Take special care to follow the warnings
indicated on the unit, as well as in the operating instructions.

1. Water and Moisture - Do not use the unit near any source of water or in excessively moist environments.

2. Object and Liquid Entry - Care should be taken so that objects do not fall, and liquids are not spilled, into
the enclosure through openings.

3. Ventilation - When installing the unit in a rack or any other location, be sure there is adequate ventilation.
Improper ventilation will cause overheating, and can damage the unit.

4. Heat - The unit should be situated away from heat sources, or other equipment that produce heat.

5. Power Sources - The unit should be connected to a power supply only of the type described in the
operating instructions, or as marked on the unit.

6. Power Cord Protection - AC power supply cords should be routed so that they are not likely to be walked
on or pinched by items placed upon or against them. Pay particular attention to cords at plugs,
convenience receptacles, and the point where they exit from the unit. Never take hold of the plug or cord
if your hand is wet. Always grasp 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 grounding-type plug.

8. Cleaning - Follow these general rules when cleaning the outside of your 1176LN:
a. Turn the power Off and unplug the unit
b. Gently wipe with a clean lint-free cloth
c. If necessary, moisten the cloth using lukewarm or distilled water, making sure not to oversaturate it

as liquid could drip inside the case and cause damage to your 1176LN
d. Use a dry lint-free cloth to remove any remaining moisture
e. Do not use aerosol sprays, solvents, or abrasives

9. Nonuse Periods - The AC power supply cord of the unit should be unplugged from the AC outlet when left
unused for a long period of time.

10. Damage Requiring Service - The unit should be serviced by a qualified service personnel when:
a. The AC power supply cord or the plug has been damaged: or
b. Objects have fallen or liquid has been spilled into the unit; or
c. The unit has been exposed to rain; or
d. The unit does not operate normally or exhibits a marked change in performance; or
e. The unit has been dropped, or the enclosure damaged.

11. Servicing - The user should not attempt to service the unit beyond that described in the operating
instructions. All other servicing should be referred to qualified service personnel.

Table of Contents

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A Letter From Bill Putnam, Jr. ................................................................................................................

Important Safety Instructions ................................................................................................................

Two Page, Two Minute Guide To Getting Started ....................................................................................

Front Panel .........................................................................................................................................

Rear Panel ...........................................................................................................................................

Interconnections ................................................................................................................................

Insider’s Secrets ..............................................................................................................................

The Technical Stuff ................................................................................................................................

History of the 1176LN ................................................................................................................

Compressor / Limiter Basics ......................................................................................................

About “All-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...................................

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The Two Page, Two Minute Guide To Getting Started
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No one likes to read owner’s manuals. We know that.
We also know that you know what you’re doing—why else would you have bought our product?

So we’re going to try to make this as easy on you as possible. Hence this two-page spread, which we
estimate will take you approximately two minutes to read. It will tell you everything you need to know to
get your Universal Audio 1176LN up and running, without bogging you down with details.

Of course, even the most expert of us has to crack a manual every once in awhile. As the saying goes,
“as a last resort, read the instructions.” You’ll find those details you’re craving—a full description of
all front and rear panel controls, interconnection diagrams, insider’s secrets, history, theory,
maintenance information, block diagrams, specifications, even a glossary of terms—in the pages that
follow.

Getting Started With Your 1176LN:

Step 1: Decide where the 1176LN is to be physically placed and 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 rear panel AC power connector.

Step 3: Mute your monitors and then, using balanced cables with XLR connectors, make connections to
the 1176LN rear panel XLR line input and output. Most often, these connections will be to a patch bay
or to and from a channel or bus insert on a mixer. (Alternatively, the rear panel terminal strip can be

used for input and output connections; see page 24 for information about its use, and  see page
12 for an interconnection diagram)

Manual conventions:

 Means that this is an especially useful tip

 Means that this is an especially important bit of information

And when we need to direct you to a page or section elsewhere in the manual, we’ll use the universal signs
for rewind () or fast forward ().

 Make only one type of input connection (XLR or terminal strip) to the 1176LN.

However, both outputs can be used simultaneously.

The Two Page, Two Minute Guide To Getting Started

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Step 4: On the right side of the front panel, depress the +4 Meter button. This not only turns on the
power to the 1176 but also ensures that the meter displays the final output level. (NOTE: Depressing
any Meter button other than OFF also has the effect of powering on the 1176LN; when powered on, the
front panel meter lights up.)

Step 5: Set the Input and Output knobs to approximately 24 (their 12 o’clock position) for unity gain.

Step 6: Set the Attack and Release knobs fully counterclockwise (in the case of the Attack knob, to its

OFF position).

Step 7: Unmute your speakers and begin monitoring the 1176LN output. At the source, raise the level
of the input signal until the 1176LN meter shows optimum signal strength (around 0 VU, with
occasional excursions into the red, but with no audible distortion).

Step 8: With the Attack knob at its OFF position, signal is passing through the 1176LN circuitry but
with a compression 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 and limiting characteristics. Note that, unlike many other devices, the 1176LN
attack and release times are faster when their associated knobs are turned clockwise, and slower
when they are turned counterclockwise. Set the Meter switch to GR in order to view the amount of gain
reduction being applied to the signal. Note that as you increase the amount of gain reduction (by
raising the Input level and/or selecting higher ratios), the overall signal may be attenuated. If
necessary, you can make up the difference by turning the Output knob clockwise. Depress either the
+8 or +4 Meter buttons in order to view the final output level. A meter reading of 0 corresponds to an
output level of either +8 dBm or +4dBm at the 1176LN output, respectively.

 For more information, refer to the “Front Panel” and “Rear Panel” sections on pages 8 - 11.

Front Panel
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(1) Input - Determines the level of the signal entering the 1176LN, as well as the threshold. Higher
settings will therefore result in increased amounts of limiting or compression.

(2) Output - Determines the final output level of signal leaving the 1176LN. Once the desired amount
of limiting or compression is achieved with the use of the Input control, the Output control can be used
to make up any gain lost due to gain reduction. To set the desired output level, press the +4 or +8
Meter button and then alter the Output knob as required. ( see #7 on page 10)

(3) Attack - Sets the amount of time it takes the 1176LN to respond to an incoming signal and begin
gain reduction. The 1176LN attack time is adjustable from 20 microseconds to 800 microseconds
(both extremely fast). The attack time is fastest when the Attack knob is in its fully clockwise position,
and is slowest when it is in its fully counterclockwise position.

(4) Release - Sets the 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 occur, due to the

rapid rise of background noise as the gain is restored. If the release time is too slow,
however, a loud section of the program may cause gain reduction that persists through a
soft section, making the soft section difficult to hear.

 Turning the Attack knob all the way fully counterclockwise (to the OFF position) disables

compression altogether; however, signal continues to pass through the 1176LN circuitry.
This is commonly used to add the “color” of the 1176LN without any actual gain reduction.

 When a fast attack time is selected, gain reduction kicks in almost immediately and

catches transient signals of very brief duration, reducing their level and thus "softening"
the sound. Slower attack times allow transients to pass through unscathed before limiting
or compression begins on the rest of the signal.

Front Panel

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(5) Ratio - These four buttons determine the severity of the applied gain reduction. (A ratio of 4:1, for
example, means that whenever there is an increase of up to 4 decibels in the loudness of the input
signal, there will only be a 1 dB increase in output level, while a ratio of 8:1 means that any time there
is an increase of up to 8 dB in the input signal, there will still only be a 1 dB increase in output level.)
When higher ratios (12:1 or 20:1) are selected, the 1176LN is limiting instead of compressing. Note
that higher Ratio settings also set the threshold higher. ( see page 20 for more information)

The 1176LN Ratio buttons allow four different modes of operation:

4 - Selects a 4:1 ratio (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 the 1176LN is in this “All-Button” mode, distortion
increases radically due to a lag time on the attack of initial transients and there are
constant changes in the attack and release times, as well as a change in the bias points.
Consequently, the meter will go wild, often resting at maximum. Don’t worry, though – you
won’t be harming the 1176LN by using this mode!

 Engineers typically use “All-button” mode on drums or on ambience or room mics. It can

also be used to “dirty” up a bass or guitar sound, or for putting vocals “in your face.”

( see page 22 for more information)

Front Panel
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(6) Meter - A standard VU meter that displays either the amount of gain reduction, or output level,
depending upon the setting of the Meter Function switch. ( see #7 below) Occasionally, the meter
may require calibration. ( see page 25 for instructions for calibrating the 1176LN meter)

(7) Meter Function – These four buttons power the unit on (or off) and determine what the 1176LN’s
front panel VU meter displays: either the amount of gain reduction (GR), or the compressor’s output
level (+8 or +4). When “+8” is selected, a meter reading of 0 corresponds to a level of +8 dBm at the
rear panel outputs. When “+4” is selected, a meter reading of 0 corresponds 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 controls to
approximately “4” (their 12 o’clock positions) so that some gain reduction is enabled.
Depress the Meter GR button so that the meter shows the amount of gain reduction, then
slowly turn the Input control up until the desired amount of gain reduction is achieved.
Finally, adjust the Attack and Release times until they are suitable for the program
material and make up any gain necessary by raising the Output knob (depress the Meter
+4 or +8 buttons to have the meter display the final output level).

Rear Panel

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(1) AC Power Connector / Fuse Holder - Connect a standard, detachable IEC power cable (supplied)
here. If fuse replacement is required, use only a 125 mA time delay (slow blow) fuse for operation at
115 V, or a 63 mA time delay (slow blow) fuse for operation at 230 V. Note that the 1176LN has no
dedicated on-off Power button; instead, depressing the Meter OFF button ( see #7 on the previous
page) has the effect of powering the unit off.

(2) XLR OUTPUT - A balanced XLR connector carrying the line-level output signal of the 1176LN. This
signal will normally be routed via a patchbay to a channel or bus insert return.

(3) XLR INPUT - Connect line-level input signal to this balanced XLR connector. Pin 2 is wired positive
(hot). This signal will normally 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 terminal for chassis ground, and the next two terminals for
output connections. The rightmost two terminals are used for connection of a remote meter. ( see
page 24 for a complete listing of all terminal strip connections) If an input connection is made to the
terminal strip, be sure that there is no connection also made to the XLR input.

(5) 1176SA connector - Used for stereo linking of two 1176LNs. ( see page 27 for stereo
interconnection instructions.)

 Never substitute different fuses other than those specified here!

 In order to avoid induced noise, make only one type of input connection (XLR or terminal

strip) to the 1176LN.

Interconnections
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 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.