Universal Audio 2-LA-2 Twin T4 User Manual
Model 2-LA-2
Twin T4 Leveling Amplifier
Universal Audio Part Number 65-00035
Universal Audio, Inc.
Customer Service & Tech Support: 1-877-MY-AUDIO
Business, Sales & Marketing: 1-866-UAD-1176
www.uaudio.com
Notice
This manual provides general information, preparation for use, installation and operating instructions
for the Universal Audio 2-LA-2 Twin T4 Leveling Amplifier.
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
© 2008 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
2-LA-2, LA-2A, LA-3A, LA-610, 1176LN, 2-1176, 6176, 2-610, 710, 4110, 8110, SOLO/2A, SOLO/110,
SOLO/610, 2192, DCS Remote Preamp, UAD and the Universal Audio, Inc. logo are trademarks of
Universal Audio, Inc. Other company and product names mentioned herein are trademarks of their
respective companies.
Thank you for purchasing the Universal Audio 2-LA-2 Twin T4 Leveling Amplifier. The 2-LA-2 takes our
LA-2A reproduction and updates it with modern features, modern components, and a space-saving
design. The LA-2A was originally produced in the early 1960s by Teletronix, which was later acquired
Contents of This Box
This package should contain:
• One 2-LA-2 Twin T4 Leveling Amplifier
• 2-LA-2 Operating Instructions
• IEC Power Cable
• Registration Card
A Letter From Bill Putnam, Jr.
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by Babcock Electronics Corporation. My father, Bill Putnam, Sr., purchased the product rights and the
name Teletronix from Babcock Engineering in 1967, folding it into his Studio Electronics Corporation
shortly before he changed the name to UREI.
The 2-LA-2 retains the same key gain reduction components and simple controls found in the LA-2A,
but adds the convenience of a stereo-matched tool made more versatile for today’s studio. It uses only
the finest audiophile quality parts, from metal film resistors and WIMA capacitors to custom input and
output transformers for an extremely low noise floor. While not an exact component clone of the classic
LA-2A, the 2-LA-2 utilizes a similar tube-amplified, all discrete design, and, like its ancestor, the
2-LA-2 compression comes from applying audio signal to an electro-luminescent light panel which
shines on a photo-electric cell, which in turn controls gain. This customized element, called the T4,
provides a dual-stage, program-dependent release time which results in extremely transparent and
natural-sounding compression.
Designed by original UREI® engineer Dennis Fink, the 2-LA-2 provides matched T4s for stereo
operation while retaining the core “sonic signature” components in order to deliver the same
trademark sound of the LA-2A long treasured by engineers worldwide. From drum bus to master bus,
vocals to vibraphones, the 2-LA-2 delivers the same authentic, smooth as silk gain reduction you’ve
come to know and trust with the LA-2A, conveniently reconfigured into a two-channel package.
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 2-LA-2 was to
build a dual/stereo compressor that we would be delighted to use ourselves—one that would capture
the character of the original LA-2A to create a device that induces that “a-ha” feeling you get when
hearing music recorded in its most natural, inspired form.
Developing the 2-LA-2—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 2-LA-2:
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 2-LA-2
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 2-LA-2 .................................................................................................................
Compressor Basics ....................................................................................................................
Electro-Optical Compression/Limiting ..................................................................................
Operating The 2-LA-2 In Link Mode .....................................................................................
Making A Custom Insert Cable ...............................................................................................
Maintenance Information...........................................................................................................
Meter Calibration ..................................................................................................
Changing the Internal Voltage Selector ......................................................................
Changing Fuses ..........................................................................................................
Block Diagram ......................................................................................................................
Glossary of Terms ..................................................................................................................................
Recall Sheet ........................................................................................................................................
Specifications ........................................................................................................................................
Additional Resources / Product Registration / Warranty / Service & Support
........................................................................................... Inside back cover
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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 2-LA-2 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, specifications, even a glossary of terms—in the pages that follow.
Getting Started With Your 2-LA-2:
Step 1: Decide where the 2-LA-2 is to be physically placed and place it there. The 2-LA-2 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: Make sure the Power switch in the center of the front panel is off (down) and then connect the
supplied IEC power cable to the rear panel AC power connector.
Step 3: Set the LINK/DUAL switch in the center of the front panel to its down (DUAL) position. Set the
LIMIT/COMPRESS switches in both channels to their down (COMPRESS) position, and set the Meter
switch for both channels to their down (OUTPUT) positions. Then turn the Gain knob to approximately 6
(unity gain) and the Peak Reduction knob to 0 (fully counterclockwise).
Step 4: Mute your monitors and then, using the appropriate cables, make connections to the 2-LA-2’s
rear panel XLR line inputs and outputs. Most often, these connections will be to a patch bay or to and
from a channel or bus insert on a mixer. ( see page 7 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 ().
The Two Page, Two Minute Guide To Getting Started
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Step 5: Power on the 2-LA-2. The purple LED above the power switch will light up.
Step 6: Unmute your monitors and apply signal to the left channel only. Slowly raise the level of the
signal being input until sufficient signal strength is achieved on the left channel meter.
Step 7: Now it’s time to hear the effect of compression on your signal. Set the Meter switch for the left
channel to its up (GR) position and, while continuing to apply input signal to the left channel, slowly
turn the Peak Reduction knob clockwise; as you do so, the left channel meter will reflect the amount of
gain reduction. You can compare the original, uncompressed signal with the compressed signal with
the use of the BYPASS/COMP switch in the center of the front panel. (NOTE: When in BYPASS mode, the
2-LA-2 does not restore signal to its original non-compressed level, so you may hear significant level
differences between the BYPASS and COMP settings if a great deal of Peak Reduction is being
applied.) As you increase the amount of compression (by raising the level of the Peak Reduction
control), the overall signal will be attenuated; turn the Gain knob clockwise to make up the difference.
Set the Meter switch back to its down (OUTPUT) position in order to view the final output level of the
left channel of the 2-LA-2 and ensure that you are applying the correct amount of makeup gain.
Step 8: Set the left channel LIMIT/COMPRESS switch to its up (LIMIT) position in order to hear the
effect of the 2-LA-2 in limiting mode, where a higher compression ratio is applied and only peak
signals are reduced in level.
Step 9: Repeat steps 6 - 8 above, this time routing signal to the right channel only and adjusting the
2-LA-2’s right channel controls as desired. Note that, in Dual mode, the two channels operate
completely independently of one another, giving you two discrete compressor/limiters.
Step 10: To hear the effect of the two compressors stereo linked, set the LINK/DUAL switch in the
center of the front panel to its up (LINK) position, and set the Peak Reduction and Gain knobs in both
channels identically. ( see page 20 for more information about operating the 2-LA-2 in Link mode)
Because the 2-LA-2 is a tube device, it needs several minutes to achieve stable operating
temperature. During warm-up, audio quality may vary slightly.
For more information, refer to the “Front Panel” and “Rear Panel” sections on pages 4 - 6
of this manual.
Because it can run quite hot, we recommend you power off the 2-LA-2 when it is not being
used for extended periods of time.
Front Panel
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Figure 1: 2-LA-2 Front Panel
NOTE: The 2-LA-2 provides two channels, each of which have identical front panel controls.
(1) COMPRESS / LIMIT switch - Determines whether the 2-LA-2 channel is acting as a compressor or
a limiter. When set to the down (COMPRESS) position, the degree of compression is gentler and at a
low ratio (approximately 4:1,program-dependent). When the switch is set to its up (LIMIT) position,
more severe compression is applied, and at a higher ratio (up to Infinity:1, again, programdependent). ( see pages 13 - 16 for more information)
(2) GR Zero Set pot - Used to calibrate the channel’s meter. ( see #3 below and page 23 for
instructions for calibrating the 2-LA-2 meter)
(3) Meter Function - This switch determines whether the channel’s VU meter displays the final output
level or the amount of gain reduction. When OUTPUT is selected (the down position), a meter reading of
0 corresponds to a level of +4 dBm at the rear panel line output. When GR (Gain Reduction) is selected
(the up position), the channel’s meter will read 0 dB when there is no incoming signal or when no
compression is being applied.
(4) Gain - Determines the final output level of the 2-LA-2 channel. A setting of approximately “6” is
unity gain. Once the desired amount of compression or limiting is set by adjusting the Peak Reduction
knob ( see #6 on the following page), the Gain knob can then be used to make up for any signal
attenuation (up to 35 dB of gain can be added). In order to have the meter display the effect of turning
the Gain knob, set the Meter Function switch ( see #3 above) to the down (OUTPUT) position.
(5) Meter - A standard VU meter that displays either the channel’s final output level or the amount of
gain reduction, depending upon the setting of the Meter Function switch. ( see #3 above)
Occasionally, the meter may require calibration. ( see page 23 for instructions for calibrating the
2-LA-2 meter)
Front Panel
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(6) Peak Reduction - Determines the amount of gain reduction provided by the 2-LA-2 channel.
This control essentially combines the Threshold, Ratio, and Input controls found on other compressors.
Higher settings will increase the relative amount of compression, while lower settings reduce the
amount of compression (a setting of 0, with the knob at its fully counterclockwise position, results in
no compression). Note, however, that all compression performed by the 2-LA-2 is programdependent—that is, the degree of gain reduction changes as the signal varies.
( see pages 13 - 16 for more information)
(7) LINK / DUAL switch - Sets the 2-LA-2 to either dual mono or stereo linked operation. When set to
the down (DUAL) position, the 2-LA-2 operates as two separate compressors, with the two channels
operating completely independent of one another. When set to the up (LINK) position, the two channels
of the 2-LA-2 act as a single stereo compressor, with equal gain reduction on both sides, even when
there is transient activity only on one channel. ( see page 20 for more information)
(8) Power - Turns the 2-LA-2 power on or off. When powered on, the purple LED immediately above the
switch lights up.
(9) BYPASS / COMP switch - Allows the gain reduction circuit to be placed in or out of the audio
path. This is useful in comparing the compressed signal to the non-compressed signal with the flip
of a switch. This is also useful if the user wishes to use the 2-LA-2 as an amplifier only, for extra
gain or tube coloration, without the compression circuit in the signal path.
The numeric values for the Gain and Peak Reduction knobs are relative scale markings
and do not represent specific dB values.
Because it can run quite hot, we recommend you power off the 2-LA-2 when it is not being
used for extended periods of time.
The BYPASS / COMP switch setting always affects both channels of the 2-LA-2,
regardless of the LINK / DUAL switch setting.
When in BYPASS mode, the 2-LA-2 does not restore signal to its original non-compressed
level, so you may hear significant level differences between the BYPASS and COMP
settings if a great deal of Peak Reduction is being applied.
When operating the 2-LA-2 in LINK mode, the Peak Reduction knobs should normally be set
to the same position in both channels. ( For more information, see page 20.)
Rear Panel
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Figure 2: 2-LA-2 Rear Panel
(1) AC Power Connector - Connect a standard, detachable IEC power cable (supplied) here. If fuse
replacement is required, use only a 1.6 A time delay (slow blow) fuse for operation at 100 or 120 volts,
or an 800 mA time delay (slow blow) fuse for operation at 240 volts.
(2) LINE OUTPUT - A balanced XLR connector carrying the line-level output signal of the 2-LA-2
channel. This signal will normally be routed via a patchbay to a channel or bus insert return.
(3) LINE INPUT - Connect line-level input signal for each channel 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.
Never substitute different fuses other than those specified here!
Interconnections
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Figure 3: Using the 2-LA-2 as a send-return processor
In the above illustration, one side of the 2-LA-2 is used as a send-return processor. Typically a
specialized send-return cable is used for this purpose ( see page 21 for more information)
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