the Maxon CP101 Compressor is an higly regarded opto-compressor. If someone is interested in analysing the circuit here it the schematic and the PCB layout.
This Schematic is for the vintage red Maxon CP101 Compressor.
The new black Maxon CP101 Compressor has the same circuit but some added features, it has a input buffer, fet switching if I recall and uses 4558 instead of 741.



