This module is intended as a companion to the stock Cherry Audio Envelope Generator.
It is intended to be even simpler to use than the stock Amplifier module. To this end, it only has a single OUT LEVEL slider and a graphically highlighted socket showing where to plug in the Envelope Generator.
If nothing is connected to the ENV IN socket, the OUT LEVEL slider acts as a straightforward attenuator on the AUDIO IN signal, from 0% to 100%.
If there is a signal connected to ENV IN, this signal will further attenuate the audio output: 0V at ENV IN will make the AUDIO OUT silent. +5V at ENV IN will make the AUDIO OUT non-inverted at the volume set by OUT LEVEL. -5V at ENV IN will make the AUDIO OUT inverted at the volume set by OUT LEVEL.
The ENV IN socket can take any voltage source - it doesn't have to be an Envelope Generator. It can be unipolar or bipolar, DC or AC, low-frequency control voltage or high-frequency audio signal. In fact, it will even operate as a precision linear ring modulator if you patch one audio source to AUDIO IN and another to ENV IN.