Future Sound Systems VAC1 Eurorack Quad VCA Module

The VCA1 Passive Optically-Controlled Attenuator, or P.O.C.A., is designed to give a set of vactrol-based gates in a compact-but-usable module. Its four gates can be set to act as low-pass-gates, or normal optically-controlled attenuators (for a “VCA” type action) via jumpers on the rear of the module. CV is normalled in a downwards fashion, so that control signals input to the top gate can effect the gate at the bottom. This is also true of the audio, but with a gate’s output normalled to the next gate’s input. This allows for steeper filtering slopes and sharper control. It is recommended, however, that only two gates are used per chain as external buffers may struggle with high impedance inputs.