Re: fuzz factory differences..wireing.

Posted by induction on Feb 18, 2015; 7:59am
URL: http://guitar-fx-layouts.238.s1.nabble.com/fuzz-factory-differences-wireing-tp17797p17801.html

Regarding the differences between layouts, for the most part, a jumper is a jumper. Consider all points connected by a jumper to be one point, and you'll get your answer. This amounts to assuming that the resistivity of a jumper is 0 ohms. This isn't entirely true, but it's pretty close when you compare it to the resistor values in the circuit. The times it makes a difference are when you want to avoid contaminating your signal with voltage surges (eg. ticking from tremolo circuits) and when you want to avoid oscillation in high gain circuits from capacitative coupling of input and output wires. It sounds like the two layouts are the same to me, but I'm basing that on your description, I haven't compared the layouts.

Don't put too much faith in the names of the controls in this (or any) pedal. The Stab pot just reduces voltage to the circuit. It's called "Sag" in many other pedals. I wouldn't expect it to stabilize anything. The Gate pot controls the gain and bias of Q2, The Comp pot controls the DC gain and bias of Q3, and the Drive pot controls the AC gain of Q3. The Volume control does actually control the output volume, but it's not wired like a standard volume control because there's DC voltage across it. You can expect most of the controls to be pretty interactive, especially because of the feedback between Q2 and Q3.

Finally, the 2n3904 is a grounded emitter gain stage. That means that its gain is controlled by the hfe of the transistor and the output impedance of whatever comes before it. The 220k is for controlling bias, not gain. If you want to reduce the gain, use a lower hfe transistor, turn down the volume knob on your guitar, or put a resistor inline with the input. You can copy the Smooth pot at the input of Fuller's version of the fuzz face (look here, near the bottom of the page) if you want to make it variable.

This circuit is fairly sensitive to the hfe of the transistors you use, and to the guitar you use it with, and it will respond very differently if there is a buffer or another pedal between your guitar and the input. Most people would want it first in the chain, but feel free to experiment.