Optical compressor reduction LED

[rschultz]

There are 2 optical compressors that have a reduction LED:
Ampeg Opto Compressor
Walrus Audio Mira

I'd like to figure out how this is done so I can add this feature to an optical compressor I'm building. Any ideas?

[Rob Strand]

The idea is simple.   There is a part of the circuit where the voltage increases with the amount of gain reduction.  You just stick an LED driver on that part of the circuit.   You will need some fiddling to get the LED brightness range right.

For optical compressors the gain reduction is the circuit is set by the drive to the opto LED.   If you added a visual LED to that part of the circuit the added LED will go brighter the harder the gain control is working.   Do not put the added LED in parallel with the existing opto LED - that's a bad solution.   How to do that depends very much on the circuit but if you have an opamp driving the opto LED through a resistor then you just add another resistor and visual LED to the same circuit.  Some circuit it's not that simple as added LED + resistor will affect the circuit.  There's no simple answer here.  You need to think about how to shoehorn the new into the circuit without affecting the operation.  In some cases adding a transistor to drive the LED might help.

As far as the basic idea goes that's about it.  The rest is implementation details, perhaps with a few headaches that need working around.

Here's an example,

[PRR]

> Walrus Audio Mira[ Invalid YouTube link ] 

This error seems to be an extra space in the URL.

https://youtu.be/jzRfJcX_bHg