Parallelyzer problems

[Wounded Paw]

So I'm trying to build a parrellel effects system for bass a la The Parallelyzer at GGG.  I've got a quad buffer that seems to work fine:



Out1 goes to the first input on a Mini Mixer from R.G. Keen but the pot is the 50K log one I have on the buffer schematic and the input caps for the mini mixer are all 10uF.



That first channel is my clean signal and that works fine by itself.  The problem comes when I plug anything into the second channel.  I just run the Out2 to the input of an existing pedal and the output of that pedal enters the mini mixer before the input cap, I'm using the volume control of the pedal itself to control levels.
At first it seems to work but then my clean signal seems to disappear whenever the pedal I've got plugged into channel 2 is turned on.  Eventually there is no sound at all when that pedal is turned on but turn it off and everything is fine again.  I have both the bypassed signal through the pedal and the clean signal through channel 1 coming out of the output of the mini mixer.  I know this because I can turn down that pot on the clean channel and the volume goes down but not off because the pedal in channel 2 is still sending it's bypassed signal through.
So the question is, what's going on?  It's got to be something to do with mini mixers seperate inputs interfering with each other.  Will using much larger resistors on the inputs and the first op-amp help or will I just loose too much signal.

Oh, and for testing purposes I just disconnected the other unused inputs on the mini mixer after their resistors, where all four meet.

[brett]

I've only skimmed your work, whicj seems logical and organised.
Perhaps you should consider whether you are mixing two signals that are out-of-phase (ie one is the electrical reverse of the other.).  Many circuits have outputs that are a modified inverse of the input. 
If this is the problem, place an inverting buffer in one of the lines.
good luck

[CGDARK]

I've only skimmed your work, whicj seems logical and organised.
Perhaps you should consider whether you are mixing two signals that are out-of-phase (ie one is the electrical reverse of the other.).  Many circuits have outputs that are a modified inverse of the input. 
If this is the problem, place an inverting buffer in one of the lines.
good luck

Yes, that could be the problem, because the majority of pedals are built to be used in series and not in parallel. For this reason, the designer usually don't care is the output signal is in phase with the input or not.

CG

[Wounded Paw]

Already thought of that.  Definitely not phasing for two reasons, it doesn't happen right away, the sound sort of fades out so I'm thinking capacitors.  And secondly the pedal I'm using for testing is a mostly standard big muff which doesn't change the phase of the signal and even if it did all the distortion would change the signal enough that it couldn't completely cancel the clean signal.  And I also tried a different experimental circuit in channel 2 and the same thing happened.

[Wounded Paw]

well adding more buffers seems to work.  if the clean channel goes through an IC buffer after the 50K pot and before the input cap on the mini mixer and the pedal goes through an IC buffer after it's output and before the input cap on the mini mixer the problem goes away.  I still don't know why it was happening which is annoying. 
Is there anything wrong with going through so many buffers?  Buffered input/splitter, buffer on the output of each channel and then combined into summing amp which is just two more buffers.  Seems excessive to me.