Beginner Fuzz Face Question

[sealyt]

Hey guys,

I recently finished my first attempt at building a fuzz pedal. I am using the Fuzz Face schematic found here: http://fuzzcentral.ssguitar.com/fuzzface/fuzzfacepnpschematic.gif with AC128 transistors. The pedal sounds very good when my guitar is at full volume, but as soon as I reduce the volume knob to 8 or 9 the fuzz disappears and it sounds like there is no pedal there at all - the guitar just sounds clean. I have double checked all the resistor values and even rebuilt the circuit but the problem persists. Everything is still on a breadboard now so its easy to change, but I can't seem to figure it out. I would appreciate any ideas you may have.

Thanks

[JustinFun]

That's the wonder and joy of a good fuzz face. It's what it's meant to do! It shouldn't be exactly as if the effect isn't on, more of a slight treble boost clean tone, but the all-out fuzz to clean tone in a slight tweak of the volume is pretty useful in my opinion, and if it doesn't do it, I assume I've done something wrong in transistor selection or biasing.

If you want to be able to vary the effect from fuzz to crunch, a series resistance on the input (eg a pot wired as a variable resistor) is a good option. Around 100k works for me.

[sealyt]

Ok cool. Nice to know its actually working properly. I will try adding a series resistance on the input and see if I like it.

Thanks for your reply.

[smallbearelec]

A couple of suggestions for optimizing the FF build:

--If you have already measured the gains and leakages of your transistors, OK. If not, you can find a method for doing that here:

http://www.geofex.com/Article_Folders/ffselect.htm

or here:

http://diy.smallbearelec.com/HowTos/FuzzFaceFAQ/FFFAQ.htm

Knowing these parameters is important to having the right device in the right position; lower gain for Q1 and higher in Q2.

--Have you tweaked the bias already? If not, some illustrations for doing it are in here:

http://diy.smallbearelec.com/HowTos/BreadboardSiFF/BreadboardSiFF.htm

The article shows silicon, but the method is the same for germanium.

Having tweaked it, a reverse audio taper pot for the fuzz will give you better control there, and JustiFun is correct that a series "cleanup" pot on the input is helpful. Again, I prefer reverse audio taper for this function.

Regards
SD

[MaxPower]

Check out the Axis Face: http://fuzzcentral.ssguitar.com/axisface.php

A modified fuzz face circuit which includes a "smoothing" pot on the input (as mentioned by JustinFun).