Manual

The Technical Stuff
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At the heart of the LA-1 was an electro-optical sensor. This was a small light-proof metal canister
which housed two components: a photoelectric cell (a light sensitive device whose electrical
resistance changes depending upon the intensity of light to which it is subjected, typically used in
the home to sense when darkness falls and then switch on lights) and a light source positioned to
shine directly on the photo-cell. Early attempts employed either neon or incandescent light sources.
Both of these took time to light up, and this delay resulted in slow attacks.
The LA-1 was not a big commercial success, but it did find its way into the hands of singing cowboy
Gene Autry, who used it extensively for his own radio and recording dates, thus helping give it a
degree of exposure and encouraging Lawrence to continue refining the design. Soon after, the LA-2
was released, with a sensor that had evolved to use an electro-luminescent panel as its light
source—a component which lit up more quickly and thus resulted in a faster attack, yielding a
gentler form of compression suitable for recording as well as broadcast applications. This sensor
was named the T4, and its development serendipitously created one of the most musically sensitive
devices to ever ride gain. ( see page 22 for more information.)
Teletronix LA-2A
Engineer Sid Feldman purchased an LA-2 early on, and soon became involved in its distribution,
selling units to numerous broadcast and recording facilities in New York and Nashville. In 1962
Lawrence began to reconfigure the LA-2 into the LA-2A, at which time the device gained a
Limit/Compress switch in response to the newfound interest from the recording industry. With its 0 to
40 dB of gain limiting, a balanced stereo interconnection, flat frequency response of 0.1 dB from 30-
15,000 Hz and a low noise level (better than 70 dB,) the LA-2A quickly became one of two industry
standard compressors (the other being Bill Putnam Sr.'s 1176)—both devices that continue to be
used extensively on recording sessions to this very day.
Teletronix became a division of Babcock Electronics Corp. in 1965. In 1967 Babcock's broadcast
division was acquired by Bill Putnam's company, Studio Electronics Corp., shortly before he changed
the company’s name to UREI®. Three different versions of the LA-2A were produced under the
auspices of these different companies before production was discontinued around 1969. However,
Putnam continued using the T4 optical detector for new designs, such as the solid-state LA-3A,
followed by the LA-4 and LA-5.
The companies that Putnam started—Universal Audio, Studio Electronics, and UREI—built products
that are still in regular use decades after their development. In 1999, Putnam’s sons Bill Jr. and
James Putnam re-launched Universal Audio. In 2000, the company released its first two products:
faithful reissues of the original LA-2A and of Bill Putnam Sr.’s 1176LN compressor. Both quickly
garnered rave reviews and both have found a home in hundreds of professional and project studios
worldwide.