Input and output caps

[colossus]

Starting down the crazy of building my own shit. I currently have a Bazz Fuss breadboarded up and I've been fiddling around with caps. At what point does the filtering of the input and output caps just become so non-existent that it's hardly making a difference? I saw on Beavis Audio that 1uf is enough to cover the entire frequency range of guitar, but then why am I seeing some builds out there with 47 uf output caps? I have 10 uf for both input and output and it sounds pretty. Or am I just totally misunderstanding what input/output caps do?

[morange]

The capacitor and the impedance following it work as a passive high pass filter. So the capacitor on the front of a fuzz face needs to be large to let any bass through, because the input impedance of that first transistor stage is low; but you could use a smaller capacitor to have the same amount of bass on something like a buffer, or fet booster, or non-inverting op-amp stage based drive effects, or a tube stage in an amplifier preamp; you know, high input impedance stuff.

For example, the cutoff frequency for the input of this is 1.59 Hz. That's way low, so this stage won't cut bass, even though the input capacitor is pretty small.

http://www.muzique.com/schem/filter.htm
http://sim.okawa-denshi.jp/en/CRhikeisan.htm

The input impedance of a bazz fuss is low, like a fuzz face, idk exactly, like around 1k. So assuming that's true, then you'd need a 100 uF capacitor for that same 1.59 Hz rolloff. But yeah I'd say 10 uF sounds like a good value.
http://en.wikipedia.org/wiki/Common_emitter
http://www.allaboutcircuits.com/vol_3/chpt_4/13.html

I think output caps are large to allow for potentially low input impedance effects to be placed after it without a huge loss in bass.

[colossus]

Thanks for the incredibly helpful explanation. I think I just need to better understand impedance.

Another related question (though perhaps more guitar than pedal oriented): Even though a guitar's frequency range goes down to only about 70hz (just kinda guessing here...), is there still a benefit of a cut-off frequency much lower than that, outside of potential w/ other instruments? I'm assuming it helps capture subsonics?

[Bellyheart]

I can't remember what I did but I made a really sweet octave down sound just changing the caps of that circuit. Think I used a big one at the end and small for input. I should figure that out again.

[Jero]

I can't remember what I did but I made a really sweet octave down sound just changing the caps of that circuit. Think I used a big one at the end and small for input. I should figure that out again.

Look up the Mongrel Fuzz. It's an octave downer made from the Bazz/BuzzBox. I have yet to try it, you reminded me.

[colossus]

Hmm that looks promising. I'm really enjoying two Bazz Fusses cascaded into each other, even without a Ge in one of the diode slots. I have a 10uf input cap on the first, then a switchable 10 uf/.47 uf for the possibility of an ultra gated sound, all output through a 47uf (cos why not). I'll probably just box it up as is with a volume knob and cap switch. Any other cool mods I'm missing out on? This has been an awesome first project.