Fuzz Face input cap(s)

[thermionix]

Was goofing around with my YAFF build, trying different input caps.  At one point I put a .47uF electrolytic in parallel with a .047uF film.

Got an octave effect!  Particularly at max fuzz settings.

What gives?

[GibsonGM]

Most likely, the octave effect was already there but was not being emphasized (happening at a low freq. trimmed by a smaller input cap), and when you changed to roughly .5u for the input cap this allowed the lower freq's to stand out, for lack of a better way to put it. 

Thus driving the trannies enough to create harmonics 2x those freq's, and you hear an octave effect...more common than it seems - you see this on oscilloscopes often as you overdrive things (tubes...) - usually they're not so pronounced it sounds just like an octave pedal - typically the octave adds to a nice shimmery sound - but sometimes....   

[digi2t]

If you have an Uglyface, try a 0.33uF or 0.47uF input cap. Sounds amazing, like an analog octave down.

[thermionix]

I'm actually using just the .047uF for the input cap.  It may seem way too small, but it sounds killer.  Still gets some mud, but just the right amount to my ears.  I also like that I'm not running signal through an electrolytic.  I can't say that I won't try other things in the future.

I guess the standard 2.2uF has a low-end rolloff that is WAY below typical guitar frequencies.  I didn't hear much difference with a 1uF, not even so much with .1uF.  I tried a .01 at one point and that was just silly.  Sounded like out-of-phase pickups.

For my Uglyface, I find the best solution is just to avoid mirrors.

[thermionix]

An update, just in case anyone's interested.  I installed a 3-way rotary switch to select input caps.  2.2uF, .47uF, and .047uF.  No octave effect in any position.

[duck_arse]

mirror, excellent. did you want the octave back?

[thermionix]

Played it again today, and it does have the octave effect with the larger input caps.  NO IDEA why I didn't hear it last night!  Maybe it was a bit cold?  Who knows.

Anyway, does this octave thing indicate a malfunction of some sort?  Like when an unstable amp gets ghost notes?  The transistors I got from Small Bear are pretty high gain.  Is that just the nature of the beast?  Do I need to move some wires around?

[thermionix]

Well I realized a Noob mistake here, I thought "YAFF" was just another way of saying Fuzz Face, didn't realize it was a specific variant.  My build I'm referencing is a traditional Ge PNP FF.

Also, the "octave" effect I'm hearing is not necessarily an octave, but some kind of ghost note.  It only appears in a limited range, say from the 7th fret to the 11th on the B string, approximately.  And only at full fuzz.  It's pretty annoying, though.

I'm using a 100K volume pot.  I tried a 500K and that got rid of most or all of the ghost note issue, but I didn't care for the sound overall.  Switched back to 100K.

I'm thinking it may be a result of my transistor gains being too high.  Has anyone else encountered this?  Is there a simple way to knock the gains down, other than using different transistors?

A few ideas come to mind, maybe someone could let me know if I'm barking up the right tree:

1) inserting a resistor between Q1E and ground
2) doing similar at Q2E or increasing fuzz pot to 2K
3) a resistor in series between battery and circuit

Any thoughts?  Thanks in advance!