Check out this article at the Geofex website, the Technology of the Fuzz Face.  It explains in depth how the circuit works:

http://www.geofex.com/Article_Folders/fuzzface/fffram.htm

Hope this helps some!
Phillip

Athens Tech (Athens Technical College) in Athens, Georgia.

Phillip

I am going to use a broad stroke to keep it basic. Transistors are kind of like transformers. The transformer has windings on both the primary and secondary. The amount of windings determines impedance. A lot means high z, less means lower z. transistors in some circles are literally called transfer-resistors, meaning from one lead to the other the resistance changes. When this change is from high to lower there is a change in signal size just like in transformers , obvious increase in gain. As gain increases- louder volume. In the fuzz face as the transistors increase in gain they go over, or over saturate in terms of how much gain they cause. It actually goes higher in gain, than it should normally. One way it is done, is on the fuzz face, the second transistors emitter or pointed lead on the schematic,(pointing inward on pnp-outward on npn)there is a 1k linear potentiometer. It is connected 1 on ground 3 on emitter or other way around, doesn't matter. This causes a stationary resistance between ground and emitter of 1,000 ohms approx. The 20uF capacitor is connected to the 2 or middle lug of the potentiometer and ground following cap polarity +/-. As the 1k pot knob is turned dc current cannot change on the emitter to ground through 1 and 3, but a small ac current can flow as there is less ac blocking ability, the capacitor sees as the lug 2 wiper is turned one way and more ac block another way. That is why the fuzz is greater and smaller as this pot is turned in one direction or another. ac actually bypasses much of this dc, causing more current flow, albeit ac current and there you have a transistor with higher total current and more ability to saturate. The gain of the whole thing is high because the input impedance is high and the outputimpedance is much lower. Also there is a feedback resistor that goes from the second transitor's emitter to the base of the first transistor, sending more dc gain to the first transistor.  But the amount of capacitance is very important. Higher cap and you see more gain, to a point. tfc.