Universal Audio LA-610 Channel Strip - Manual (Page 17)

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does not control the input level, but rather controls the amount
of side chain gain applied to the input signal.
Side-Chain Circuit
The previously described gain reduction circuit is controlled by the control voltage which
is supplied by the side-chain circuit. The LA-610 is a feed-back style compressor. This
is due to the fact that the signal that is used to drive the side-chain circuit is affected by
the gain reduced signal. This signal is first fed into the side-chain drive circuit and in
turn controls the compression threshold and amount of gain reduction. A 12AX7 is then
used as a voltage amplifier to increase the signal level. A pre-emphasis circuit is
provided on the output of the 12AX7. Originally designed for broadcast, the LA-2A
allowed for side-chain equalization, which allowed the operator to make the compression
more or less sensitive to the voice frequency bands. For musical applications, this
equalization is usually set to a flat frequency response. The LA-610 does not have this
feature and is preset for music applications
Historical Notes
The 610 Preamp
Bill Putnam was awarded the 2000 Technical Grammy for his multiple contributions to
the recording industry. He was highly regarded as a recording engineer, studio
designer/operator and inventor. Putnam was considered a favorite of musical icons
including 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 were an experimentation ground for his continuing desire to push the envelope.
Universal in Chicago, United and Western in Los Angeles (now Ocean Way and Cello)
all preserve elements of his room designs.
The companies Putnam started, Universal Audio, Studio Electronics, and UREI, built
products – mostly of his design – that are still in regular use decades after their
development.
In 1999 Bill and James Putnam re-launched Universal Audio to reproduce classic analog
recording equipment designed by their father and others. In a short time the company has
released two reproductions, the 1176LN and Teletronix LA-2A compressors, designed
the 2-610, a new mic-pre inspired by a classic, acquired a company (Kind of Loud
Technologies), and launched Powered Plug-Ins, the first in the Universal Audio Digital
product line. Whatever the endeavor, every project taken on by the UA team is driven by
it historical roots and a desire to wed classic analog technology with the demands of the
modern digital studio.
The 2-610 was inspired by the Putnam-designed 610 console built in 1960 for his United
Recording facility at 6050 Sunset Boulevard in West Hollywood (now Ocean Way). As
was the case with most of Putnam’s innovations, the 610 was the pragmatic upshot of a
recurring problem in the studio: how to fix a console without interrupting a session. The
traditional console of the time was a one-piece control surface with all components
connected via patch cords. If a problem occurred, the session came to a halt while the