Problem with some of the classic opto compressor designs is slow attack and release time. NSL-33-007 optocoupler has fast rise and decay time. With fast optocoupler attack and release can be controlled almost entirely with the sidechain.
https://mm.digikey.com/Volume0/opasdata ... 33-007.pdf
Here's asidechain I came up with
RV1 = Threshold
RV2 = Release
RV3 = attack
RV4 = Ratio
Design of the amplifier part should be fairly trivial. Balanced line receiver at the input, series resistor and LDR to ground, make up gain and DRV134 output.
OPTO compressor design
Moderator: Heikki