MXR Dyna Comp Conversion into Line Level Compressor

jensenmann said:

There´s a bit of a level and impedance mismatch in your basic idea.
Your D/A offers low output impedance and high output level. It´s a line level signal hence spits out close to 15V peak at 0dBFS (depending on your settings). Your dynacomp has an high impedance input but it´s made for guitar level signals which is not exactly defined but something between 0,1V-1V. For that purpose you´d need a stepdown transformer which lowers D/As output voltage. Try something like 4:1 or even higher ratio. An input transformer will give you debalancing for free which is great.
Your dynacomp runs of 9V single rail supply. If you feed it with maximum input voltage it will give you roughly 4V peak at the output. What you need now is to bring these 4V back up to line level. You´d need a voltage gain of 15/4=3,75. Unfortunately the output impedance in a dynacomp is pretty high which means you cannot drive a stepup transformer with it. There are two solutions:
1. what you did, using a stepdown tranny to balance the signal, lower output impedance and voltage to microphone-level and then use a micpre to bring the voltage back up to your desired level.
2. Use an output buffer instead of the output transformer. A buffer can be designed with enough gain to bring the voltage up and additionally balance the signal or drive a transformer for balancing. Having the output voltage adjustable would be a handy feature which could be implemented, too.

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