LA-2A Leveling Amplifier


The LA-2A Leveling Amplifier is an audio compressor invented by James F. Lawrence II, founder of the Teletronix Engineering Company in Pasadena, California in the early 1960s. Teletronix was sold to Babcock Electronics of Costa Mesa, California in 1965. In 1967 Studio Electronics, picked up Babcock's broadcast division, including the Teletronix brand. Three versions of the LA-2A were made until 1969. The LA-2A was inducted into the TECnology Hall of Fame in 2004.
The LA-2A is a hand-wired, tube-based compressor. It uses an electroluminescent panel together with a cadmium-sulfide light dependent resistor to provide gain reduction, which in the LA-2A's own terminology is called the T4 cell. The properties of the T4 give the LA-2A its unique character by making it an entirely program dependent design. The average attack time is 10 milliseconds, while the release time is about 60 ms for 50% release and 0.5 to 5 seconds for full release, depending on the previous program material.
The LA-2A has simple controls: a Peak-Reduction knob controls the gain of the side-chain circuit, and therefore, the gain reduction; a Gain Control for make-up gain; and a Limit/Compress switch which alters the compression ratio. The VU meter may also be switched to show the gain reduction or output level.
The LA-2A has a sonic character that makes it sought after by many recording engineers.