Doepfer A-132-1

Module A-132 (Dual Low Cost VCA) contains two voltage controlled amplifiers, with a linear response most suited to regulating the level of control voltages (ADSR amount, level of vibrato effect, etc.).
In non-critical situations, though, its VCAs can be used to control audio signals.
Amplification is governed by the sum of the voltages patched into the two CV inputs.

Remark: The A-132 is able to process even slowly varying control voltages (DC coupled in/outputs).