Universal Audio LA-610 User Manual
Model LA-610
Mk II
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 LA-610 Mk II.
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
LA-610 Mk II, LA-610, 2-610, LA-2A, 2-LA-2, 1176LN, 6176, 4110, 8110, SOLO/610, SOLO/110, 710
Twin-Finity, DCS Remote Preamp, 2192, 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 Mk II version of the LA-610 Channel Strip. The LA-610 is a vacuum tube
device that combines a modified channel of our 2-610 microphone preamplifier with an LA-2A style
optical compressor. The LA-610 Mk II is a second-generation product from the original 2005 design,
with new user-requested features such as true compressor bypass, larger metering, increased output
signal, an auto-sensing power supply, and the highly popular “black on black” appearance of the LA610 Signature Edition. The preamp and compressor are identical to the original LA-610 that users have
come to know and love.
Contents of This Box
This package should contain:
• One LA-610 Mk II Tube Preamplifier / Compressor
• LA-610 Operating Instructions
• IEC Power Cable
• Registration Card
A Letter From Bill Putnam, Jr.
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The 2-610 was inspired by the microphone preamp section of the original 610 console designed by my
father, M.T. “Bill” Putnam, in 1960. The 610 was a rotary-control console and it was also the first
console of a modular design. Although technologically simple compared to modern consoles, the 610
possessed a warmth and character that kept it in demand for decades. A prominent component of my
father’s United/Western Studios in Los Angeles, the 610 was used on many classic recordings by
Frank Sinatra and Sarah Vaughan, as well as the Beach Boys’ Pet Sounds and the Doors’ LA Woman.
The compressor section in the LA-610 utilizes circuit components that are virtually identical to those
in the famed LA- 2A compressor, used on countless recordings for more than fifty years. The heart and
soul of the LA-2A is mostly a result of a special optical gain control element called the T4, and its
uniquely musical response, treasured by engineers the world over, is present in the LA-610 as well.
However, the LA-610 offers an even wider variety of tone and sonic character by virtue of its dual
stage level controls and EQ section. The versatility of the LA-610 lies in its ability to serve as a mic
or instrument preamp with or without EQ and compression. What’s more, the LA-610’s line level input
allows it to be used as a dedicated compressor with or without EQ and tube saturation.
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 LA610 was to build an integrated mic preamp / compressor that we would be delighted to use
ourselves—one that would capture the original character of the 610 and LA-2A to create a device that
induces that “a-ha” feeling you get when hearing music recorded in its most natural, inspired form.
You’ll find that the controls of the LA-610 are simple and essential: we added only those features
required for practical use without needless duplication of functionality found elsewhere in most
studios. The end result is an outstanding yet easy-to-use product that combines a legendary mic
preamp with a legendary optical compressor, making for a sound that is truly extraordinary.
Developing the LA-610—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 - The unit should be cleaned only as recommended by the manufacturer.
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 610 .....................................................................................................
LA-610 Overview.........................................................................................................
Compressor Basics ...................................................................................................
Electro-Optical Compression/Limiting .........................................................................
LA-610 Circuit Details.....................................................................................................
About Class A ...........................................................................................................
About Negative Feedback ...........................................................................................
Impedance Matching .....................................................................................................
Phantom Power .........................................................................................................
Maintenance Information...............................................................................................
Meter Calibration ............................................................................................
Internal Power Fuse ........................................................................................
Changing Tubes ............................................................................................
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 LA-610 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 LA-610:
Step 1: Decide where the LA-610 is to be physically placed and place it there. The LA-610 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: Mute your monitors and then, using a balanced cable with XLR connectors, connect the
LA-610’s rear panel line output to the appropriate input on your patch bay, mixer, or DAW.
Step 3: Set all three switches on the left side of the front panel to their down position, ensuring that
the -15 dB pad is not engaged, that the signal is in phase, and that no phantom power is being
applied.
Step 4: Connect the desired input source to the LA-610’s rear panel balanced XLR mic or line input,
or to the front panel unbalanced ¼" jack Hi-Z input. (see page 5 for more information, and
see page 9 for an interconnection diagram)
Step 5: Make sure the Power switch on the right side of the front panel is off (down) and then connect
the supplied IEC power cable to the rear panel AC power connector.
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 6: On the left side of the front panel (preamp section), turn the Level control to its minimum
(fully counterclockwise) position and set the Gain control to 0 (center position).
Step 7: On the right side of the front panel (compressor section), set the Peak Reduction knob to 0
(fully counterclockwise) and set the Mode switch to BYP (bypass). This bypasses the gain reduction
and makeup gain functionality of the LA-610. (see page 6 for more information ) Finally, set the
Meter switch to PREAMP so that it shows the output level of the signal leaving the LA-610 preamp
section.
Step 8: Power on the LA-610. The jewel light to the left of the power switch will light up.
Step 9: If a microphone requiring 48 volts of phantom power is connected to the LA-610, turn on the
+48V switch (up position).
Step 10: Unmute your monitors. Use the LA-610 front-panel Input Select switch to select the
connected source and then apply input signal while slowly increasing the Level control to
approximately 7. You should now be hearing signal.
Step 11: While watching the LA-610 meter, set the preamp Gain switch (on the left side of the front
panel) so that sufficient signal strength is achieved.
Step 12: Experiment with differing degrees of preamp Gain and Level to hear the various amounts of
coloration the LA-610 can impart to your signal. For the cleanest, most uncolored signal, set the Gain
switch to its lowest usable setting with Level set between 7 and 10. If you hear distortion even at the
lowest Gain level, employ the -15 dB pad to reduce the input level. If you are using a connected
microphone or Hi-Z instrument input, experiment also with various impedance settings to achieve
optimum tonality for your source signal.
Step 13: Experiment with the effect of the LA-610’s high and low shelving filters on your source
signal.
Step 14: Now it’s time to activate the T4 Optical compressor section of the LA-610 on the right side
of the front panel and explore its controls. Begin by setting the Meter to GR (Gain Reduction) and the
Mode switch to COMP (Compression) and then slowly turn the Peak Reduction knob clockwise to hear
the effect of the optical compressor on your signal. Note that as you do so, the LA-610 meter reflects
the amount of gain reduction. Note also that as you increase the amount of compression (by raising
the level of the Peak Reduction control), the overall signal may be attenuated. If necessary, you can
make up the difference by turning the compressor Gain knob clockwise from its unity gain position
(approximately 6). Change the Meter switch to COMP in order to view the final output level. A meter
reading of 0 corresponds to an output level of +4dBm at the LA-610 output.
Step 15: Set the Mode switch to LIMIT in order to hear the effect of the optical compressor in limiting
mode, where a higher compression ratio is applied and only peak signals are reduced in level.
Because the LA-610 is a tube device, it needs several minutes to achieve stable operating
temperature. During warm-up, audio quality may vary slightly.
Front Panel
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(1) Gain - Adjusts the gain of the input stage in stepped 5 dB increments. Turning the Gain switch
clockwise raises the gain. Because this also has the effect of reducing negative feedback ( see
page 24), the Gain switch also alters the amount of the input tube’s harmonic distortion, a major
contribution to the “warm” sound characteristic of tube equipment. The higher the Gain setting, the
more coloration the LA-610 will impart to the incoming signal.
(2) Input Select - Determines which of the following three inputs is active: Mic, Line, or Hi-Z.
The Mic and Hi-Z inputs each provide two different impedance settings.
Mic - Selects the input signal coming from the rear panel balanced XLR MIC INPUT
connection. ( see #3 on page 8) The impedance for the Mic input can be set to 500 ohms
or 2.0K ohms. Switching between these two positions while listening to a connected
microphone may reveal a different tonal quality and/or gain difference (be sure to carefully
level-match when doing comparisons because louder tends to sound better). Typically, a
microphone preamplifier should have input impedance roughly equal to about 10 times the
microphone output impedance. For example, if your microphone has an output impedance of
approximately 200 ohms, the switch should be set to the 2.0K position. However, making
music is not necessarily about adhering to technical specifications, so feel free to
experiment with the settings to attain the desired sound: you will not harm your microphone
or the LA-610.
Line - Selects the input signal coming from the rear panel balanced XLR LINE INPUT
connection. ( see #2 on page 8) This connection has an input impedance of approximately
13K ohms and is intended to accommodate mixers, DAWs, tape machines, other mic
preamps, signal processors, or any device with a line level output, such as keyboards, sound
modules and drum machines. Using this input, the LA-610 can act as a “tone box” for line-
level signals, offering a variety of sonic colors based on front panel control settings.
The LA-610 MkII makes improvements over the orginal LA-610 with regard to the accuracy
of the stepped Gain switch’s presented dB value. (for example, -10 dB truly is -10 dB).
Front Panel
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Hi-Z - Selects the input signal coming from the front panel unbalanced ¼" jack Hi-Z
connection. ( see #6 below) Intended for the direct connection of electric guitar, electric
bass, or any instrument with a magnetic or acoustic transducer pickup, this can be set to
either 47K ohms or 2.2M ohms. The 47K ohms setting is best suited for the -10 dBv level
signals typically provided by active basses and guitars, while the 2.2M ohms setting is more
suitable for instruments with passive pickup systems. Since a particular instrument’s output
impedance may actually be somewhere between the active and passive levels, feel free to
experiment to achieve the best sound at the desired level. ( see page 24 for more
information)
(3) -15 dB PAD - Reduces the mic input signal by -15dB. (This switch has no effect on Line or Hi-Z
signal.) Use this to reduce the incoming signal in cases where undesired distortion is present at low
gain levels (for instance, where especially sensitive microphones are used on loud instruments).
(4) Polarity - Determines the polarity of the LA-610’s LINE OUTPUT. When IN ø is selected (the
normal position most of the time), the signal is in phase, and pin 2 is hot (positive). When OUT ø is
selected, the signal is out of phase, and pin 3 is hot (positive). Polarity reversal may be useful in
cases where more than one microphone is utilized in recording a source.
(5) +48 V - Most modern condenser microphones require +48 volts of phantom power to operate. This
toggle switch applies 48 volts to the LA-610 MIC INPUT when the switch is up (in the +48V position).
( See page 25 for more information about phantom power)
(6) Hi-Z Input - Connect high impedance signal from an instrument such as electric guitar or bass to
this standard unbalanced ¼" jack connector. If a connection is made to the Hi-Z input, be sure that
there is no connection also made to the Mic or Line inputs.
(7) Level - Determines the amount of signal sent to the final preamp output stage. For the cleanest,
most uncolored signal from the LA-610, set the Gain switch ( see #1 on page 4) to a low setting (10 or -5) while turning the Level knob until the appropriate output signal is attained.
Keep phantom power off (switch down) when it is not required.
To avoid loud transients, always make sure phantom power is off when connecting or
disconnecting microphones, and mute speakers.
Always check the power requirements of your microphone with the manufacturer before
applying phantom power.
The LA-610 Mk II differs from the orginal LA-610 with the tube used at the preamp output
stage, and now uses the 12AT7 just like the 2-610, SOLO/610 and 6176. This is a by-product
of the newly implemented “true bypass” for the LA-610 Mk II, making the preamp section
identical to its cousins when in bypass.
Front Panel
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(8) High Boost/Cut - Selects the amount of cut or boost applied by the high shelving filter. The
positive and negative numbers on the front panel denote dB values (-9, -6, -4.5, -3, -1.5, 0, +1.5, +3,
+4.5, +6, +9).
(9) High Frequency – In conjunction with the High Boost/Cut switch ( see #8 above), selects the
corner frequency for the high shelving filter. Available frequencies are 4.5K (kHz), 7K (kHz), and 10K
(kHz).
(10) Low Boost/Cut - Selects the amount of cut or boost applied by the low shelving filter. The
positive and negative numbers on the front panel denote dB values (-9, -6, -4.5, -3, -1.5, 0, +1.5,
+3, +4.5, +6, +9).
(11) Low Frequency - In conjunction with the Low Boost/Cut switch ( see #10 above), selects the
corner frequency for the low shelving filter. Available frequencies are 70 Hz, 100 Hz, and 200 Hz.
(12) Peak Reduction - Determines the amount of gain reduction provided by the T4 Optical
compressor. 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 LA-610 is
program-dependent—that is, the degree of gain reduction changes as the signal varies.
( see pages 18 - 22 for more information)
(13) Gain - Once the desired amount of compression or limiting is set by adjusting the Peak
Reduction knob, the Gain knob can be used to make up for any signal attenuation (up to 20 dB of gain
can be added). Set the Meter Function switch to the COMP position in order to have the meter display
the final output level from the LA-610 when adjusting the compressor Gain knob. ( see #14 below)
(14) Meter Function - This switch determines what the LA-610’s VU meter displays: either the
PREAMP output (that is, the level of the signal which feeds the compressor section), the amount of
compressor gain reduction (GR), or the LA-610’s final output level, after compression (COMP). When
COMP is selected, a meter reading of 0 corresponds to a level of +4 dBm at the rear panel line output
jack.
A compressor Gain setting of approximately 6 is unity gain (no signal boost or attenuation).
When the T4 compressor is bypassed, “GR” and “COMP” settings will not show activity.
Front Panel
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(15) Mode - A three-position switch which sets the compression section into either Bypass mode
(BYP), Compression (COMP), or Limiting (LIMIT). When the switch is in the COMP position, the degree
of compression is gentler and at a low ratio (approximately 3:1, program-dependent). When the switch
is set to the LIMIT position, there is more severe compression, and at a higher ratio (up to ∞:1,
again, program-dependent). ( see pages 18 - 22 for more information)
(16) Meter - A standard VU meter that displays either the preamp section output, amount of gain
reduction, or final output level, depending upon the setting of the Meter Function switch.
( see #14 on page 6) ( see page 25 for instructions for calibrating the LA-610 meter)
(17) Power - Turns the LA-610 power on or off. When powered on, the jewel light immediately to the
left of this switch is lit.
The LA-610 Mk II differs dramatically from the original LA-610 when the unit is in Bypass
mode (BYP). With the original, even when the LA-610 was set to BYPASS mode, incoming
signal continued to pass through the compressor section. For that reason, the compressor
Gain control remained active. The LA-610 Mk II has true bypass, which completely removes
the T4 Optical Compressor section, including its makeup gain control and GR/COMP
metering.
The LA-610 Mk II uses a larger, and better-lit, easier to read meter than its predecessor.
The meter is lit with LEDs, so no bulb will ever need replacing. The improved meter
electronics means a highly stable meter with no drift.
Unlike the original LA-610, the LA-610 Mk II uses an LED to illuminate the power jewel light.
Therefore, no bulb will ever need replacing.
The audible difference between compression and limiting on the T4 compressor can be quite
subtle. Greater audible differences are more easily detected on transient-rich sources, and
when a large amount of gain reduction is applied.
The LA-610Mk II gives the user 15 dB of additional gain above other 610 products through
the makeup gain of the T4 compressor (a total of 77 dB). Turn off Peak Reduction for when
maximum gain is needed such as with low-output ribbon microphones.
Rear Panel
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(1) LINE OUTPUT - A balanced XLR connector carrying the line-level output signal of the LA-610. Note
that Pin 2 is positive when the front panel Polarity toggle switch is down (IN ø). Pin 3 is positive
when the front panel Polarity switch is up (OUT ø). ( see #4 on page 5)
(2) LINE INPUT - Connect line-level input signal (coming from a device such as a mixer, DAW, tape
machine, or signal processor) to this balanced XLR connector. Pin 2 is wired positive (hot).
(3) MIC INPUT - Connect your microphone to this standard XLR connector. Pin 2 is wired positive
(hot).
(4) AC Power Connector - Connect a standard, detachable IEC power cable (supplied) here. The LA610 can operate from 100V to 240 VAC / 50-60 Hz. The internal power supply is self-sensing and will
automatically work throughout this voltage range. ( see page 26 for more information)
Unlike the original LA-610, the LA-610 Mk II uses an internally switching power supply. The
unit may be used in virtually any part of the world with no need to worry about the incoming
voltage.
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