A Voltage Controlled Amplifier (VCA) in a modular synthesizer is used to control the amplitude, or loudness, of an audio signal. It works by accepting a control voltage (CV) input, which is used to control the gain (amplification) of the audio signal. The output of the VCA is the amplified audio signal.
Linear and logarithmic responses refer to the way in which the VCA responds to the control voltage. A linear response means that the gain of the audio signal increases or decreases at a constant rate as the control voltage increases or decreases. A logarithmic response means that the gain of the audio signal increases or decreases at a non-constant rate as the control voltage increases or decreases. Logarithmic responses are often used in VCAs because they mimic the way the human ear perceives loudness changes.
Several types of VCAs can be used in a modular synthesizer, each with its own unique features and characteristics. Here are the main types of VCAs in order of their