Operating instructions

The Technical Stuff
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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 designer/operator and inventor,
Putnam was considered a favorite of musical icons Frank Sinatra, Nat King Cole, Ray Charles, Duke
Ellington, Ella Fitzgerald and many, many more. The studios he designed and operated were known for
their sound and his innovations were a reflection of his desire to continually push the envelope.
Universal Recording in Chicago, as well as Ocean Way and Cello Studios (now EASTWEST) in Los
Angeles all preserve elements of his room designs.
In 2005, in collaboration with Dennis Fink, one of the original UREI® analog design engineers,
Universal Audio released the LA-610, which has been carefully designed to deliver the essence of the
“LA” sound but without the costs of being an exact LA-2A component clone. The LA-610 uses three
tubes for warmth and overall tonal balance. After the preamp section, the LA-610 offers a new optical
compressor, based upon the original T4 circuitry, and the same easy-to-use controls provided by the
LA-2A.
We here at Univeral Audio, have two goals in mind: to reproduce classic analog recording equipment
designed by Bill Putnam Sr. and his colleagues, and to design new recording tools in the spirit of
vintage analog technology. Today we are realizing those goals, bridging the worlds of vintage analog
and DSP technology in a creative atmosphere where musicians, audio engineers, analog designers
and DSP engineers intermingle and exchange ideas. Every project taken on by the UA team is driven by
its historical roots and a desire to wed classic analog technology with the demands of the modern
digital studio.
LA-610 Overview
The LA-610 is a vacuum-tube channel strip that combines a microphone/instrument/line preamplifier
with an optical compressor/limiter.
Its creation was based on a simple idea: Put a T4 compressor circuit in the output section of our 610
mic preamp. This effectively marries two faithful reissues of vintage audio devices long revered by
engineers the world over. The 610 has a long lineage of its own, based upon the original 610 console
built by Bill Putnam Sr. Similarly, the T4 houses the electroluminescent panel and photo-resistors that
characterise the signature sound of the famed LA-2A.
The function of a preamplifier, as its name implies, is to increase (or amplify) the level of an
incoming signal to the point where other devices in the chain can make use of it. The output level of
microphones is very low and therefore requires specially designed mic preamplifiers to raise their
level to that needed by a mixing console, tape recorder, or digital audio workstation (DAW) without
degrading the signal to noise ratio. This is no simple task, especially when you consider that mic
preamps may be called upon to amplify signals by as much as 1000%.
Accomplishing musical-sounding compression is no simple task, and a number of different circuits
have been developed through the years to attain that goal. One of the most unique of these circuit
designs is the electro-optical one created for the LA-2A (and employed by the LA-610), where
incoming signal varies the strength of a light shining on a light-sensitive cell that is controlling
overall gain. This has the desirable effect of making the compression entirely program-dependent
(that is, the