Help with Fuzz circuit Bias

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sonolink

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Feb 15, 2010
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I've breadboarded the classic NPN Fuzz Face circuit and it sounds great although a bit limited for my taste. So after reading the articles on Fuzz Central about several mods I began by replacing Q2 collector resistor with a 10k pot. The pot is a great add-on but I feel that half of the range of the pot is useless. All the changes, from sputtery to fully open happen in a very short portion of the turn of the pot, if you know what I mean.
I tried with other values, basically what I had at hand (25k, 50k and 100k) but it's pretty much the same. Am I guessing right if I think that I should lower the resistance of the pot to be able to use the whole turn or should I combine the pot with another fixed resistor?
Any help/ideas are very welcome, thanks :)

The classic FF NPN circuit:

fuzzfacenpnschematic.gif

The modded FF circuit:

axisfacesi3schematic.gif
 
Hey John,
Thanks for your reply. That's exactly what I'm trying to do :)
But I'm asking for help to exploit the full turn of a pot. I must be doing something wrong or not understanding how it works, hence some ideas/advice on that would be great ;)

Cheers
Sono
 
All the changes, from sputtery to fully open happen in a very short portion of the turn of the pot

Linear or logarithmic taper? You could try the opposite taper of whatever you are currently using to see if it gives a more usable adjustment range.
You may also need to connect a series resistor to the pot so that you have a minimum resistance and can't get all the way to 0 collector resistance.
 
Linear or logarithmic taper? You could try the opposite taper of whatever you are currently using to see if it gives a more usable adjustment range.
You may also need to connect a series resistor to the pot so that you have a minimum resistance and can't get all the way to 0 collector resistance.

I'm using linear. I'll try a resistor in series beginning with 1K and see what it gives.

Thanks! :)
Sono
 
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