The original Gain Brain from Allison Research, introduced in 1971, was a FET (field effect transistor) compressor/limiter. The circuit was completely re-designed around the new Valley TA101 VCA, the result became the Valley People-branded Gain Brain II variable ratio limiter.
The Gain Brain is a dynamic unit using a proprietary design for the gain reduction element. Unlike a regular Peak or RMS detector, the Gain Brain's detector employs the principle of linear integration which varies the response of the detector based on the waveform complexity. The more complex waveforms are allowed to pass through the detector at a slightly higher absolute level compared to simpler waveforms, thus yielding a more musical response. Another important feature is Valley People's peak reversion correction circuitry which accurately compensates for the loss of low frequencies - a problem usually associated with convential compressor designs.
Despite it's highly compelx design, the unit offers traditional controls including Threshold, a variable Ratio ranging from 1.3:1 to infinity:1, a Gain control, an Attack knob ranging from 0.2 to 200 milliseconds and a Release from 0.05 to 5 seconds. What's more, the Release can be set to linear or logarithmic mode, which aids a more musical response in sources with a wide dynamic range.
The Gear Rack