Fuzz Face Filter Questions

[mr_fender]

Hey all,

I've been building pedals for a while, but I'm trying to learn more about the how and why part.  I'm trying to better understand the filters in the Fuzz face circuit and had a couple of questions.

Using the filter calculator at Muzique.com, I plugged in the values for the input high pass filter of the Fuzz face circuit.

Input cap = 2.2uF
Resistance to ground = 101k (100k feedback resistor + 1k fuzz pot)
I get a cutoff frequency of 0.7 Hz.  This seems way low to me, so I'm not sure if I'm doing this right.

I did the same for the output high pass filter:

Output cap = 0.01uF
Resistance to ground = 500k (volume pot)
I get a cutoff frequency of 31.8 Hz.  This seems reasonable as it allow nearly all of the bass frequencies out.

I was also looking at the Axis Face circuit and comparing the differences.  The Axis Face has a 0.22uF input cap in order to roll off more of the boomy lows in the circuit.  However plugging in the figures to the calculator:

Input cap = 0.22uF
Resistance to ground = 101k (100k feedback resistor + 1k fuzz pot)
I get a cutoff frequency of 7.2 Hz.  This is still WAY below the audio spectrum, so how can this reduce any bass in the circuit.

I feel like I'm missing something here.  Please help.

Thanks

[oskar]

Reduce the input cap. Halving it should double the f_c ( cutoff frequency )!

And don't forget to vote SLEIPNER in this month's FX-X!   

skar

[petemoore]

  Kudos for trying to do math, I try once in a while also, good excersize whether I get it right every time or not.
  7hz is almost DC, I guess those caps values in the positions they are cutoff bass higher than that, especially the .01uf's mentioned.
  The high freq's may get attenuated by the transistors, especially Ge's, that's why fairly often you'll see LP filtering in an Si FF.