Universal Audio LA-3A User Manual
Model LA-3A
AUDIO LEVELER
Universal Audio Manual Number 65-1301
Revision 1.53
IMPORTANT SAFETY INSTRUCTIONS
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.
Water and Moisture - Do not use the unit near any
1.
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 groundingtype 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. Carts and Stands - The unit should be used only with a
cart or stand that is recommended by the manufacturer.
The unit and cart combination should be moved with
care. Quick stops, excessive force and uneven surfaces
may cause the unit and cart combination to overturn.
9. Wall Or Ceiling Mount - The unit should be mounted to a
wall or ceiling only as recommended by the
manufacturer.
10. Cleaning - The unit should be cleaned only as
recommended by the manufacturer.
11. 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.
12. Damage Requiring Service - The unit should be
serviced by a qualified service personnel when:
The AC power supply cord or the plug has
•
been damaged: or
Objects have fallen or liquid has been spilled
•
into the unit; or
•
The unit has been exposed to rain; or
•
The unit does not operate normally or exhibits
a marked change in performance; or
•
The unit has been dropped, or the enclosure
damaged.
13. 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.
Notice
This manual provides general information, preparation for use, installation and operating instructions for the Universal
Audio LA-3A Audio Leveler. 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 © 2005 Universal Audio, Inc.
All rights reserved. This manual and 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
LA-2A, LA-3A, 1176LN, 2-610, 2108, 6176, 2-1176, LA-610, 4110, 8110 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.
THE LA-3A AUDIO LEVELER
Thank you for purchasing the LA-3A Audio Leveler. The LA-3A is a solid-state version of Universal Audio’s
vacuum tube based Teletronrix LA-2A, and was designed by Brad Plunkett. In it’s day, the LA-3A was considered an improvement over the LA-2A because it eliminated “noisy tubes” and maintenance issues. Today, both
products are revered for their smooth and musical control of audio levels. Engineers choose the LA-2A or LA-3A
based on the different sonic character each one offers.
The T4 Compressor elements in the LA-3A are identical to the circuit components housed inside the T4
optical cell used on the legendary LA-2A compressor. The heart and soul of the LA-3A is mostly a result of this
special optical gain control element. When rst developed in the early 1960’s, the electro-luminescent optical
gain reduction was quite revolutionary: applying the audio signal to an electro-luminescent light panel which
shines on a photo-electric cell which in turn controls the gain. In contrast to the electro-optical devices that
preceded it, the electro-luminescent light source provided the fast attack necessary for broadcast applications.
Additionally, the cadmium-sulde photocells provided a very natural “two-stage” release, which resulted in a
compression characteristic more transparent than the other compressors of the day. The LA-3A features handwired components and two simple front panel controls. Its ease of operation and signature tone make it a rst
call for vocals, guitars and just about any application where an ultra fast release time is not needed.
In addition to the LA-3A and Teletronrix LA-2A Leveling Ampliers, Universal Audio has released reproductions of the classic 1176LN Limiter as well as the 610 tube preamp and 2108 microphone preamplier. UA
also offers several channel strips and “2 pak” units based on these vintage circuits. In addition, the 4110 and
8110 Precision Microphone preamps deliver ultra high performance clarity utilizing modern capacitor free JFET
circuits. Universal Audio also creates software emulation’s of our vintage hardware that run on our UAD-1 DSP
card as well as Digidesign’s Pro Tools platform. All of these products are designed to meet the demands of the
modern recording studio, yet retain the character of vintage equipment. Please visit www.uaudio.com to see
and read about other great recording tools from Universal Audio.
Once again, thank you for supporting Universal Audio. We hope our products bring inspiration to your musical
endeavors.
Universal Audio, Santa Cruz, California
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TABLE OF CONTENTS
LA-3A SPECIFICATIONS 3
LA-3A FRONT PANEL 4
Peak Reduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Gain. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Meter Function. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Meter Calibration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
LA-3A REAR CHASSIS 5
Limit/Compress Switch. . . . . . . . . . . . . . . . . . . . . . . . . 5
50/30 dB Gain Switch. . . . . . . . . . . . . . . . . . . . . . . . . . . 6
MOD Gain Switch. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Stereo ADJ Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
High Frequency Contour Control. . . . . . . . . . . . . . . . . . 6
Input/Output XLRs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
AC Power. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Fuse/Mains. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Voltage Select. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Unbalanced Connections. . . . . . . . . . . . . . . . . . . . . . . . 7
Balanced Connections. . . . . . . . . . . . . . . . . . . . . . . . . . 7
Chassis Ground. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
STEREO OPERATION 7
Rear Chassis Link Connections. . . . . . . . . . . . . . . . . . . 7
Stereo Setup / Calibration. . . . . . . . . . . . . . . . . . . . . . . 8
Stereo Use. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Applications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Control Settings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
WHAT COMPRESSORS DO 9
Attack and Release. . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Compressing Vocals. . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Bass Guitar. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Any Sound. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Tricks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
RACK MOUNTING 10
Single Unit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Instructions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Dual Unit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Instructions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
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COMPRESSOR THEORY OF OPERATION 12
Compressor Basics. . . . . . . . . . . . . . . . . . . . . . . . . . . 12
The T4 Cell. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Side-Chain Circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
HISTORICAL NOTES 16
The 610 Preamp. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Classic Compressors. . . . . . . . . . . . . . . . . . . . . . . . . . 17
The 1176 LN. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
The LA-2A. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
RECALL SHEET 19
2
LA-3A SPECIFICATIONS
Balanced Line Input Impedance. . . . . . . . 600Ω oating
Max. Input Level. . . . . . . . . . . . . . . . . . . . -0dBm @ 50dBm gain setting
Internal Output Impedance. . . . . . . . . . . . 600Ω oating
Maximum Output Level. . . . . . . . . . . . . . . +20 dBm nominal, 27 dBm max. peaks
Internal Output Impedance. . . . . . . . . . . . approximately 50Ω
Recommended Minimum Load. . . . . . . . . 50Ω
Frequency Response. . . . . . . . . . . . . . . . . 20 Hz to 20 kHz +/- 0.5dB
Maximum Gain. . . . . . . . . . . . . . . . . . . . . 50 dB +/- 1 dB
Noise Floor. . . . . . . . . . . . . . . . . . . . . . . . . -80 dB @ limiting threshold
Distortion. . . . . . . . . . . . . . . . . . . . . . . . . < 0.35% THD @ +24 dBm
Max Gain Reduction. . . . . . . . . . . . . . . . . 40 dB
Attack Time. . . . . . . . . . . . . . . . . . . . . . . . 1.5ms or less, program dependent
Release Time (stage 1). . . . . . . . . . . . . . . 60 ms (50% release)
Release Time (stage 2). . . . . . . . . . . . . . . 0.5 to 5 seconds, program dependent
General
Power Requirements. . . . . . . . . . . . . . . . . 115V / 230V operation
Fuse (115V use). . . . . . . . . . . . . . . . . . . . 3AG 1/8amp TD (slow blow)
Fuse (230V use). . . . . . . . . . . . . . . . . . . . 3AG 1/16 amp TD (slow blow)
Max. Power Consumption. . . . . . . . . . . . . 35 Watts
Dimensions. . . . . . . . . . . . . . . . . . . . . . . . 3.5” vertical (2RU), 1/2 19” rack, 9.25” depth
Weight. . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5 lbs. (boxed, 11 lbs.) Dual LA-3A, 13.0 lbs. (boxed 19 lbs)
Warranty. . . . . . . . . . . . . . . . . . . . . . . . . . 1 year, parts and labor (go to www.uaudio.com for details)
3
LA-3A OPERATING INSTRUCTIONS
GR OU TPU T
PO WER
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GAIN
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REDUCT ION
UNIVERSAL AUDIO, INC. SANTA CRUZ, CALIFORNIA
The LA-3A is a solid state compressor that automatically reduces the level of loud signals in order to maintain
a more consistent volume level, void of loud peaks that can cause unwanted clipping and associated distortion. For the remainder of this manual, the more common term “compressor” will be used instead of “leveling
amplier” or “audio leveler”.
LA-3A FRONT PANEL
This panel has the GAIN knob, analog meter, PEAK REDUCTION knob, meter function switch (GR / OUTPUT),
meter ZERO SET control and the POWER ON switch. Each control is discussed in the following sections.
Peak Reduction
The PEAK REDUCTION control determines when the compressor receives a signal “loud” enough to trigger gain
reduction as well as total output level. Higher settings will increase the relative amount of compression. The
GR / OUTPUT switch below the GAIN knob should be set to GR to view the amount of gain reduction the LA-3A
is doing. We recommend adjusting the PEAK REDUCTION control until the meter reads between -3 and -5 on
the meter during volume peaks. NOTE: adjusting the level of the device that’s plugged into the LA-3A input as
well as adjusting the PEAK REDUCTION control knob can affect the amount of compression. Heavily compressed
signals can be made louder by increasing the GAIN knob just to the left of the meter. See “Side Chain Circuit”
on page 14 for technical details.
Gain
The GAIN control behaves like an output level control. Turning this control clockwise will increase the output
level of the signal at the output jack on the rear panel, typically feeding a mixing console or recording device.
The GR / OUTPUT switch below the GAIN knob should be set to output to view signal strength on the LA-3A meter. When the LA-3A is in deep compression, signal level is reduced. The GAIN knob is used to restore the signal
level.
Meter Function
The LA-3A VU meter can be used to indicate compressor gain reduction or nal output level. The meter
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