Circuit Crosstalk on Breadboard

[oliphaunt]

I have a si NPN Fuzz Face and a SHO on my breadboard right now, sharing the same power supply.  Running the input/output to either one by themselves works great, no issues.  But when I split the input signal so that they both have an input but the output is on the SHO I get crosstalk from the fuzz over at the output of the SHO.  Even if I simply run a jumper wire from in to out and bypass the boost entirely I get the same thing, as long as I split the input signal and the fuzz gets an input it ends up in the output.  

I am working on a way to split the input signal and process each side in parallel and then recombine then.  The cross talk ruins the processing on one side though.  How can I solve this?

[ianmgull]

Generally to run effects in parallel you'll want to put a buffer before them, and some sort of mixer afterward. There is a good article over at GeneralGuitarGadgets.com about parallel processing. The problem arises with the fact that your Fuzz Face will likely not play well with a buffer. There may be a solution but I've never tried it. That is to use a pickup simulator in front of the Fuzz Face and after it's buffer. I'm pretty sure there is an article about this at AMZ.

[zachary vex]

That's actually not crosstalk.  Fuzz Faces have very low input impedance and it actually changes as the wave switches from up to down.  This causes the signal at the input to be damaged by the Fuzz Face.  Imagine you're manually entering a waveform into a lever on a machine, and as you swing it up and down, it jerks suddenly on your arm at a certain position every time.  Now, your waveform is damaged by the machine no matter what you do.  If you attach a clean machine to your hand at the same time the clean machine will reproduce the damaged wave no matter what you do, because now your arm is being jerked around.

[oliphaunt]

Thanks Mr. Zach, that makes some sense to me.  I tried putting a buffer before the boost but that made no difference.  Is there anything else I can do to solve this damage from the FF?  I can use a different circuit for the distortion side of my processing, but I really hoped to use the FF...

[dschwartz]

ground the input of one fuzz while using the other

[oliphaunt]

ground the input of one fuzz while using the other

Thanks but I am not using two effects at different times.  In this case I am trying to create a fuzz for bass where I split the signal, then process one side with the fuzz face and keep the other half dry.  I will run them through a crossover and re-combine the two for a full, dry low end with fuzzy top.  

[earthtonesaudio]

Put a resistor in series with each effect's input.  10k for each resistor may be enough to isolate them from each other.  If you put a buffer first, then split to two 10k resistors, that would almost guarantee to eliminate the problem.