ANYONE HAVE A BREADBOARD HANDY ?

[Dragonfly]

I'm 1200 miles away from home, so no breadboard available. Anyway, here's a simple overdrive/distortion circuit schematic...i'm curious as to the sound..."mainly" how the 100pF cap affects the sound . If you have a breadboard and a few parts (even "close" values should be fine), i'd be curious to hear your thoughts...

just wondering,
  AC

[sfr]

Just tossed this together, now I need to find something to plug into it, and something to plug it into (gig last night, everythings in the car) will report back in a bit.

[sfr]

A rather mild distortion - a little rougher than I'd consider "overdrive", but not enough of it to really call it "distortion" either.  Cleans up nicely with the volume on the guitar or dialing back the "gain" knob.  Seems like a moderate but not huge volume boost over the unaffected signal, but with no bypass on my breadboard and no A/B box, I can't be 100 certain. 

Seems a little on the muddy side, but I don't know how much of that is the shitty practice amp I grabbed.  Having that 100pf cap in, taking it out, and swapping it for 220pf and 500pf all sound about the same.  Having a cap in there does seems to tame the muddyness of it a little bit, particularly on bass guitar.  (It does get a very cool farty sound on bass) Having the cap also seems to add a more distortion to it.  Upping the value to 500pf and it sems get a little more "clippy", loses some sustain. 

I'll try it with a different amp later this afternoon. 

[petemoore]

  placing a B/C cap should rolloff highs, before the clipping / diodes.

[sfr]

Correct - I had the toggles on my switch confused.

[alextheian-alex]

it rolls off some highs... it is waaaaay up around 60kHz though, so it really just acts like a RF filter.  You can increase it to about 1000p before you dip into the guitar freq range, and over a few thousand or so pF if you want to roll off some treble.

Evaluation of the circuit:
Gain pot:
Range of gain is 12dB
-3dB low cutoff @ gate is 40Hz at min and 140Hz at max
-3dB low cutoff @ output is 74Hz at min and 140Hz at max
Clipping is assymetrical, with a hard clip on the negative side