[sdiy] adding compressor to mix bus

[Erik Dower]

So I'm inserting a Cwejman VC-FCS stereo compressor into the stereo bus of my mixer, but I haven't been able to quite get it right. For context sake, this is a DJ mixer that I've integrated into my suitcase style DIY performance modular synthesizer.  Unfortunately I can't just run the output of the mixer through the compressor as I need to be able to use the headphone cue system AND hear the compressed signal!

Right now it works but there is too much noise when turned up loud.  By noise I mean oscillator bleed, ground noise etc., and it's there even with nothing connected to the input.  

Here's the schematic for the mixer summing stage (U1B):

http://www.dspaudio.com/mixsum.jpg

I've cut the trace after pin 7 and used that point to send to and return from the compressor.  

The return from the compressor is also going through a buffer with no output impedance in order to match the expectations of the mixer.

If I remove the compressor from the insert point and just run it into the regular inputs of the mixer it's nice and clean, but once inserted again I get the noise.

Any suggestions are greatly appreciated!

Thanks!

epk