biasing a fuzz

[Chickenwings]

Why do some of the sexy fuzz faces like the sunface have a single bias control, whereas if you look inside any of the dunlop fuzz faces (hendrix etc), underneath the circuit board there are TWO bias trimpots? Why do they have 2? Which one do you adjust to get the smoother or more splattery sound?

 

[ratherdashing]

Re: biasing a fuzz

A FF has two transistors, each with a bias resistor. Dunlop probably uses trim pots so they can manually (and precisely) set the bias on both in the factory.

The bias on the first transistor will have the greatest effect on the tone, so that's probably the one you'd want a bias knob on.

 

[Chickenwings]

Re: biasing a fuzz

so is the sundial the equivalent of the first trimpot?

 

[ratherdashing]

Re: biasing a fuzz

so is that the same one as the sundial knob?

I don't know enough about the Sunface to say for certain, but I'd guess that the sundial knob is the bias for T1.