Voltage Controlled Amplifier
VCA 424 provide voltage-controlled amplification.
The amount of amplification the VCAs provide is determined by the voltage at the CV input, and the position of the gain control, which sets the overall gain in the system.
The VCA has 4 audio inputs, each with an attenuator. They are amplified by an amount determined by the combination of the gain and the 4 CV controls. OTA based.