Noodling with the feedback resistor in a Fuzz Face

[mordechai]

I swapped out the typical 100K feedback resistor for a 68K between Q1 and Q2, and my fuzz face seemed to get quite a bit more "hair", in a good way.  Can someone explain what is happening with this change that led to the apparent increase in gain?

[Mark Hammer]

You probably want to look at the Technology of the Fuzz Face paper over at Geofex.

I'll note in passing that this resistance is made variable in the Z-Vex Wooly Mammoth, and provides useful changes in overall distortion character.

[petemoore]

  150k, tall with a pot on it or otherwise adjustable.
   Of course there's one in the Tonebender, and it is a good R-position to 'set personally' or make adjustable depending on...what it depends on soundwise etc.

[seedlings]

That's a negative feedback resistor, so decrease it to lower gain of your transistors.  Maybe you found stumbled on to the 'magic' gain ratio with your setup.

CHAD

[mordechai]

That's a negative feedback resistor, so decrease it to lower gain of your transistors.  Maybe you found stumbled on to the 'magic' gain ratio with your setup.

CHAD

So if I'm understanding you correctly -- in a PNP Fuzz Face, a 100K feedback resistor between the base of Q1 and the emitter of Q2 will yield MORE gain than a feedback resistor of 68K?  I remember someone posting here that when you increase the resistor, you might increase output but you DECREASE gain...