The Doepfer A-131 is a exponential voltage controlled amplifier (VCA) module for the Eurorack A-100 series. The A-131 has been designed to deal specifically with audio signals (the A-130 is usually used for linear signals). The Gain knob sets the overall level for the system output. The A-131 features two audio inputs, each with its own attenuator and are amplified by an amount determined by the combination of the gain and the CV controls.