Cap values on overdrive/distortion pedal

[Joecool85]

I'm building a pedal that I designed, so far so good.  It sounds great, but a little heavy.  Right now I am using .1uf caps for both the in and outputs.  I've noticed most pedals use smaller caps for output compared to that of the input.  Is that important?  I'm thinking of picking up some .047, .022 and .01 caps to play with but I wanted some opinions specifically on the ratio of input cap value:output cap value.

[petemoore]

  In/Out caps means we talke of rolling off bass.
  If you let lots of low end into your FF, say with a 4u7 input cap, the amp will be processing more signal and bass tends to load it more than treble. Artifacts of the low frequencies will also be created in the process, using a large output cap would let them out, using a small one would limit what is let out, but the frequencies it passes may be altered by the circuts processing of the 'added' content let in by the incap.
  In a clipping circuit this can make a difference. In a circuit with plenty of headroom I think mostly increased bass response would be the result of larger valued series signal path caps.

[Joecool85]

So...does that mean that I should have a larger one for input than output or just play with it till I like the sound?

[MartyMart]

So...does that mean that I should have a larger one for input than output or just play with it till I like the sound?

I would say in general, reduce the input cap so that you're not "distorting" loads of
low end "mud" ( unless you have serious roll off at the gain stage anyway ? )
I tend to go with input caps of 10n to 47n and out caps of 100n for opamp type
distortion/overdrive
Works for my setup, but "FF's" are a different beast !
MM.

[Joecool85]

FFs are a totally different beast lol.  Looks like having something around .047uF sounds pretty good, .01uF was too trebley, I might try a .022 later though.  But before I do too much more I need to get some more sustain out of this beast.  The tone is fine, the sustain is only a shade better than clean.  I think I'm going to throw in a 2n3904 with a 1n914 diode before the rest of the circuit, and then use the ground on that to control gain instead of controlling it in the second stage.

[petemoore]

 that's about what I use, for input 47n, and out caps of 100n
 Does heavy rock 'Mash' [bass notes 'melt'] with .22uf or even .1uf input cap though.

[Joecool85]

does 1n = .01uF?

[mojotron]

does 1n = .01uF?

.001uF

What I do to tweak out the mud (and/or add clarity/tone), assuming you have 2+ stages - this might apply, is to use a 470pF cap in parallel with a 1M pot (16mm Alpha) - and I put this parallel cap/resistor compo in series with the input and 2nd stage to form a filter as seen on the Blue Magic (http://www.generalguitargadgets.com/diagrams/bmagic.pdf) using components C6 and R6. Except I substitute a 1M pot for the 470k resistor.

What this does is it gives you a high pass filter such that when the pot is closer to 1M less lower frequencies are passed and when the pot is close to 0 ohms you have more of an all-pass filter. What I have found is that 470pF/470K is pretty good for a pre-distortion filter to prevent distorting low-end mud...

This is not a good technique to use if you don't have an input stage that gives you 10+ in gain - like on most diode clippers. But - you can also add something like a fetzer valve as an input stage if needed - but that is making some substantial changes...