Proper biasing of the Germanium transistors found in Synthrotek’s Fuzz Face clone and the Face the Fuzz pedals is essential to getting the best (optimal) tone out of your product. We want to take a moment here to explain how you can do this on your own for both the kit version and completed versions. These instructions should also help with other Fuzz Face clones as well.
Synthrotek is now testing and bias testing all of the Germanium transistors that we send with kits and completed units. We choose optimum gain for Q1 and Q2 to make sure that proper biasing is possible. Completed pedals are biased before and after installation into the PCB to help make sure that you have a great sounding pedal upon initial use. Even though we do this, it is important to know how to do this on your own, as Germanium transistors are very sensitive to temperature changes and will need to be re-biased now and again. Since both kits and completed pedals both come with bias tested transistors, you should not need to completely remove the electronics from the housing. The trimmer resistor can be dialed in by ear to suit the desired tone if you so desire. This information is for those seeking precision.
For the Fuzz Face circuit to be optimally biased, the collector of Q2 needs to be at 4.5 volts. (When connecting the Arbiter Fuzz Face Clone circuit to your multimeter as shown in the photos below your meter will read -4.5v) The 20K trim pot is used to dial in this value. You will need a multi-meter that reads DC voltage to accomplish this, which can be found very inexpensively at places like Harbor Freight Tools. All you need to do is connect your leads to a ground on the PCB and the collector of Q2 to get this reading. (Pedal must be powered on)
We have made two graphics below showing you how to do this for both the Fuzz Face clone (which powers off the negative rail), and our new Face the Fuzz pedal which powers off a standard 9V center negative supply and can be daisy chained with other 9V center negative pedals.