Universal Audio LA-610 Channel Strip User Manual
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The LA-2A
The LA-2A leveling amplifier, a tube unit with hand wired components and three simple
controls, was introduced in the mid 1960s. It utilized a system of electro-luminescent
optical gain control that was quite
revolutionary; gain reduction was controlled by
applying the audio voltage to a luminescent driver amplifier, with a second matched
photoconductive cell used to control the metering section. 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 below plus 10 dBm output,) the LA-
2A quickly became a studio standard. Originally patented by Jim Lawrence, it was
produced by Teletronix in Pasadena, California, which became a division of Babcock
Electronics Corp. in 1965. In 1967 Babcock's broadcast division was acquired by the
legendary 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.