Input or Output Capacitor??

[Sparky]

Getting an even, balanced tone from lows to highs without woofy lows or piercing highs.  Is it better to modify the signal coming in or going out??

[GGBB]

Coming in or going out of what?

[FiveseveN]

Well you've set yourself up with a false dichotomy (input and output caps are not the only ways to "modify the signal"), an ill-defined goal (balanced tone is a matter of taste, genre, context, practicalities etc.) and as GGBB pointed out, left out arguably the most important piece of the puzzle.
I'm going to assume it's some kind of distortion, and the effects of pre- and post-distortion filtering have been covered here many times. I also remember a video from Brian going over some of these aspects:

I'd say get a breadboard and swap out some time constants for the particular circuit you're interested in. Alternatively or additionally you can use DAWs or editors or standalone pedal and ampsims to get a more general grasp on gain staging and filtering in your signal chain, lots of free options nowadays.

[Sparky]

Yup, should have stipulated Fuzz Face or Tonebender  [2 transistor] circuit.  Ideally I would try out my builds in a live band situation but situations don't permit that.   Listening to the results of experimentation indoors is tricky when not mixed in with other instruments.   There are lots of ways to EQ and modify the sound of a guitar, amp, or pedal but right now I'm simplifying the process and will work within the confines and limitations of the capacitors.   Personal experiences from other guitarists will be a good start.

[Rob Strand]

Playing with the input caps will sets how much the pedal farts out with the bass strings.   Playing with the output caps tunes the overall lows.    With small amounts of roll-off (ie. low cut-off frequencies) it can be hard to discern between the two.   In a band setting more people would go for roll-off at the input.

A good experiment is to set-up a switch which selects cut using the input *or* the output cap.  For tune the caps so the sound is close in both positions.   Then put the pedal through it's paces.  On the one you dislike try a cap up or down of the current value.  Does that change the status quo?   Now can you tune the other cap to make it sound better?

Even that test needs help because it's rarely true that the best sound come from filtering at the input and none at the output (ie. big cap), or visa versa.    You end-up tweaking both caps to get the best sound whatever way you go.   If you wanted to add a low-cut switch on top of that "best" set-up I'd say the selecting the input cap would win out.

It can take hours of work.  Then when you plug everything into another rig and the decision points change!!

[Sparky]

Playing with the input caps will sets how much the pedal farts out with the bass strings.   Playing with the output caps tunes the overall lows.    With small amounts of roll-off (ie. low cut-off frequencies) it can be hard to discern between the two.   In a band setting more people would go for roll-off at the input.

A good experiment is to set-up a switch which selects cut using the input *or* the output cap.  For tune the caps so the sound is close in both positions.   Then put the pedal through it's paces.  On the one you dislike try a cap up or down of the current value.  Does that change the status quo?   Now can you tune the other cap to make it sound better?

Even that test needs help because it's rarely true that the best sound come from filtering at the input and none at the output (ie. big cap), or visa versa.    You end-up tweaking both caps to get the best sound whatever way you go.   If you wanted to add a low-cut switch on top of that "best" set-up I'd say the selecting the input cap would win out.

It can take hours of work.  Then when you plug everything into another rig and the decision points change!!

Yeah...it's that hours of work that I'd like to minimize!   A few years ago somebody said to change all the caps to  either .33 uf or  ,033 or .003 uf.    I haven't done that yet.  Something else I haven't tried yet is   minimizing the input cap  [ .0033 ??] and then making the output cap  1.  or larger.     

[andy-h-h]

Yup, should have stipulated Fuzz Face or Tonebender  [2 transistor] circuit.  Ideally I would try out my builds in a live band situation but situations don't permit that.   Listening to the results of experimentation indoors is tricky when not mixed in with other instruments.   There are lots of ways to EQ and modify the sound of a guitar, amp, or pedal but right now I'm simplifying the process and will work within the confines and limitations of the capacitors.   Personal experiences from other guitarists will be a good start.

For a fuzz face style circuit - and this is a simple answer:  change the input cap.  The output cap is already kind of small.  The input cap is large by comparison

Analog man uses a 1u input cap as an example.   

[iainpunk]

maybe its worth experimenting with the gain capacitor as well. it kind of limits the gain at lower frequencies instead of cutting them on the way in, and it also linearizes the transfer at low frequencies somewhat.

i'd start at the original 2.2uF, and go down in 3rds of a decade, so 1uF, 470nF 220nF 100nF 47nF etc... and then finetune when you have found the range you like.

cheers

[Sparky]

maybe its worth experimenting with the gain capacitor as well. it kind of limits the gain at lower frequencies instead of cutting them on the way in, and it also linearizes the transfer at low frequencies somewhat.

i'd start at the original 2.2uF, and go down in 3rds of a decade, so 1uF, 470nF 220nF 100nF 47nF etc... and then finetune when you have found the range you like.

cheers

I have an original vintage-correct silicon Fuzz Face with factory original BC 108C  transistors  [also with the stock 2.2 uf  input cap.]    I use this as a point of comparison to my other builds.  It's basically great for all the Hendrix / Trower  type stuff but is way too bass-heavy for mixing with other instruments.  There is a wall of mud that washes over everything .   I have started messing around with the Tonebender circuit again to see how it works in real-world band situations .   It is basically less gain and less overall bass than a FF so it fits in the mix better.  It came before the FF and can be heard in lots of 1960's British  stuff before Hendrix jumped on the FF.    Certain transistors can be less treble heavy than others so it's always interesting to see how they will function in the circuit.  [ My focus is on silicon trannies]  So, yeah, plenty of other factors involved with shaping the sound of a pedal!