question on bypass cap for fuzz face 1k pot

[bobster]

hi folks,
ive built a f/f with nkt271s salvaged from old junk. its soundin not too bad but very bassy even with in and out cap changes. with gtr vol full up its stupid fat and wooly. i have read that you can put a bypass cap on the fuzz control??
can anyone advise what would be a good value of cap to try and what lugs on the fuzz pot would i solder to?
thanks - bob

[BAARON]

A standard Fuzz Face already has an electrolytic cap attached to the middle lug of the fuzz control.  Making that cap smaller (4.7µF or 10µF, for example) will tighten up the bass response a bit.

What values have you tried for input and output caps?

[bobster]

hi.
ive tried 0.5 uf on input and 2 uf on output.
tonight i tried turning fuzz pot a bit lower which has helped with worst excess of bass wooliness. i upped the 330ohm to about 900ohm and levels are good. im getting close to a sweet spot now but theres a fair amount of hiss probably cos of the old germaniums.
might try a big cap on power rails and see if that helps
bob

[BAARON]

I use 0.22µF (1/10th the original size) on the input and 0.01µF (that's the stock value) on the output.  If you're actually using 2µF on the output, that's going to be letting through way more bass than stock... the default 0.01µF output cap in a Fuzz Face helps control the bass output of the effect a little bit with a 500k volume pot, and quite a bit with a 100k volume pot.

Fuzzes hiss.  Germanium apparently hisses more.  One thing that will calm some of your hiss (and might smooth the clipping out a little bit) is putting tiny caps across the collector/base junctions of Q1 or Q2, or across the 33k resistor on the collector of Q1... try 47-150pF for any of the positions to help eliminate some of the hiss and smooth things out a little bit.

[zombiwoof]

Yup, a .01uf cap was stock on the old FF's, some of the schems going around say .1, but they are wrong.  Even my red Dunlop FF had the .1uf cap in it, when I replaced it I got rid of the overpowering bass going on.  There is a bypass cap you can put across the volume pot, it works just like a treble bypass cap in a guitar, helps retain the treble at lower than maximum volume settings.  I got the idea when looking at a schematic for Roger Mayer's FF circuit, there was an .002 uf cap across the volume pot, so I tried it on my FF and it worked.  You might want to experiment with different values to dial it in if you want to do it.

Al

[bobster]

thanks guys-
i just worked out i do have an 0.01 cap in circuit for output   . the one i thought was output cap and changed to 2uf was the 20uf electro cap so maybe it doesnt affect the sound.
i might try these little trimmer caps you suggest across the 33k and / or the vol pot. ive put a 100k pot on volume now and its a little better with that.  the sound with guitar down a bit is really nice
bob

[BAARON]

thanks guys-
i just worked out i do have an 0.01 cap in circuit for output   . the one i thought was output cap and changed to 2uf was the 20uf electro cap so maybe it doesnt affect the sound.
i might try these little trimmer caps you suggest across the 33k and / or the vol pot. ive put a 100k pot on volume now and its a little better with that.  the sound with guitar down a bit is really nice
bob

Yeah, I did the math last night and realized that you'd have to make the 22µF cap quite a bit smaller for it to start affecting the frequency response.  2.2µF won't be much of an audible difference, but you might actually start to notice a change if you go down to 1µF or even 0.47µF.

If you like the sound with your guitar's volume rolled down, a trick you can do is to wire a 100k pot in series with the input (connect the wire coming FROM the footswitch to the pot's middle lug, and the effect's input cap to the right-hand lug when you're looking at the back of the pot).  Turning that pot up will smooth the fuzz out in much the same manner as turning your guitar volume down will, and then you won't have to worry about turning down your guitar's volume knob every time you turn on your fuzz pedal.  Think of it as a "smooth" control.  It's an easy mod, and it's worth trying, I'd say!

[bobster]

hey thanks again for the tips.
i put in a 50 k pot [ thats all i had ] as a pre gain i think its called. it appears to be wired like you describe above and does help .
maybe 100k will be better?
i'll get one next time im in town.
im gonna try this box at a gig tonight for the first time with the nkt271s. i had bc109s in before as neg ground but it was just too fizzy and nasty although did clean up well. i think the 271s are getting me closer to the jimi sound which i like being a strat player.
bob