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.[1] Teletronix was sold to Babcock Electronics of Costa Mesa, California in 1965. In 1967 Studio Electronics (eventually renamed UREI), picked up Babcock's broadcast division, including the Teletronix brand. Three versions of the LA-2A were made until 1969.[2] The LA-2A was inducted into the TECnology Hall of Fame in 2004.[3]

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,[4] 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.[5]

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.

LA-2As warm things up. ...they EQ all the warmth and low mids and bass. When you put bass and drums in them they get fatter and bigger. And unless you hit them way hard and make the tubes sizzle they don't really distort.

— Jim Scott[2]

See also
  • The LA-3A, a transistorised version of the LA-2A
  • The 1176 Peak Limiter, another popular vintage compressor descended from the LA-2A

References
  1. http://www.uaudio.com/blog/la-2a-analog-obsession
  2. "Archived copy" (PDF). Archived from the original (PDF) on 2006-11-13. Retrieved 2009-03-11.CS1 maint: archived copy as title (link)
  3. "Archived copy". Archived from the original on 2008-09-27. Retrieved 2008-08-25.CS1 maint: archived copy as title (link)
  4. https://www.uaudio.com/webzine/2003/june/text/content4.html
  5. JBL vintage service manuals. UREI LA-2A service manual. "This Instruction Book was reprinted from text composed by the original manufacturer (complete with errors and exaggerations; for example, the specification for attack time should have been in milliseconds rather than microseconds." Retrieved on October 11, 2009.


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