The VCA (Voltage Controlled Amplifier) sets the volume of a signal from a control voltage. Without it, an oscillator would play nonstop: the VCA, driven by an envelope, is what makes each note start and die away.
Inputs
- In: the signal whose volume you set (often the filter output).
- CV: the volume control, from 0 V (silence) to 10 V (full volume). With no cable on CV, the VCA lets everything through.
Output
- Out: the amplified signal.
Controls
- Level: overall volume, from 0 to 1, applied on top of the control voltage.
- Lin/Exp: the shape of the response. In linear, 5 V gives half the volume; in exponential, the curve sags much more and fades sound more natural to the ear, which hears volume on a logarithmic scale.
Why it matters
The "oscillator → filter → VCA" trio driven by an envelope is the heart of subtractive synthesis. The VCA can also shape any control signal: an LFO sent through a VCA driven by an envelope gives a vibrato that fades in little by little.
Try this in the inspector
Watch the Out output while you play a short note: the scope shows the wave swelling, then dying away with the envelope. Turn Lin/Exp from one end to the other and hear the tail of each note get softer.