Mos Face

[Sparky]

More fuzz and volume than a stock Fuzz Face or Tonebender.   I'm playing around with input and output caps as well as a Gagan input control instead of the stock fuzz pot.  There is more treble, also, and could stand to be tamed down a bit..

[Rob Strand]

I spent some time experimenting with this version about 20 years ago.   If I remember correctly the pedal doesn't sound bright as such but you get a kind of subtle fizz in the upper treble frequencies.  Despite that the MOSFET designs have a little less presence than the transistor versions.   I didn't try to remove that as many MOSFET designs have that characteristic.

You could try adding a cap to ground from where R2 and R3 join to ground, perhaps start around 22n and increase or decrease to taste.    Another way is to add a small cap across the drain and gate of the MOSFET, perhaps start around 47pF and increase or decrease to taste.    You might find the second method messes with the character of the sound more and perhaps doesn't remove the upper frequencies as well.

[Mark Hammer]

My own build has toggles to change the input capacitor value, the feedback resistor (R4), and current-limiting resistance from V+, in addition to the two pots.  A lot of different sounds available.

[Sparky]

My own build has toggles to change the input capacitor value, the feedback resistor (R4), and current-limiting resistance from V+, in addition to the two pots.  A lot of different sounds available.

I've seen some mutant FF circuits [ Colorsound 1 Knob Fuzz]  with 150 k feedback resistors....wouldn't this increase the amount of distortion in the circuit??
I think the Tonebender  [2 transistor] has a 47 k in there..
Putting a lower hfe transistor in Q1 takes some high-end out of the circuit but that sort of takes away from the "high gain" aspect of the pedal.
The input pre-gain control adds some variations in the tone and volume combinations that the original fuzz control lacks.  Gagan's idea came along before the Fuller pedal by the way. 

[Mark Hammer]

I've seen some mutant FF circuits [ Colorsound 1 Knob Fuzz]  with 150 k feedback resistors....wouldn't this increase the amount of distortion in the circuit??
I think the Tonebender  [2 transistor] has a 47 k in there..

Ever since I saw the "Pinch" control in the ZVex Woolly Mammoth (which varies that feedback resistance in what is essentially a Fuzz Face optimized for bass), I've tinkered with that resistance value whenever possible.  It interacts with the gain control setting, and is able to yield "zipper" and gated sounds.  Worth playing with.  Whatever the stock value is, consider upping it by 2x or 3x.

[soggybag]

Take look at Tim Escobedo's "Many faces of fuzz". There are a few fuzz face variations using BJT, MOSFET, and JFets.

[Rob Strand]

R4 loads the pickup, that can drop the highs going *into* the pedal.

R4 also has some complex behaviour because AC signals at the emitter of Q2 can mess with the bias of Q1 - that happens more when the fuzz control is backed off.

[Sparky]

I've seen some mutant FF circuits [ Colorsound 1 Knob Fuzz]  with 150 k feedback resistors....wouldn't this increase the amount of distortion in the circuit??
I think the Tonebender  [2 transistor] has a 47 k in there..

Ever since I saw the "Pinch" control in the ZVex Woolly Mammoth (which varies that feedback resistance in what is essentially a Fuzz Face optimized for bass), I've tinkered with that resistance value whenever possible.  It interacts with the gain control setting, and is able to yield "zipper" and gated sounds.  Worth playing with.  Whatever the stock value is, consider upping it by 2x or 3x.

I can see that this could get out of control really fast if I get too experimental about it.   It's such a simple circuit that it's too easy to change just one resistor.

[Sparky]

Take look at Tim Escobedo's "Many faces of fuzz". There are a few fuzz face variations using BJT, MOSFET, and JFets.

Thanx for reminding me about the Escobedo variations.  I remember them from years ago..

[Sparky]

I've seen some mutant FF circuits [ Colorsound 1 Knob Fuzz]  with 150 k feedback resistors....wouldn't this increase the amount of distortion in the circuit??
I think the Tonebender  [2 transistor] has a 47 k in there..

Ever since I saw the "Pinch" control in the ZVex Woolly Mammoth (which varies that feedback resistance in what is essentially a Fuzz Face optimized for bass), I've tinkered with that resistance value whenever possible.  It interacts with the gain control setting, and is able to yield "zipper" and gated sounds.  Worth playing with.  Whatever the stock value is, consider upping it by 2x or 3x.

It never ends!    Thanx!

[mac]

You could try adding a cap to ground from where R2 and R3 join to ground, perhaps start around 22n and increase or decrease to taste.

You can replace R2 with a 1K-B pot and put a 22n to 100n cap from pin 2 to Vcc, or Gnd --> treble cut

           R2  1K-B          R3             
Vcc ------/////////-------///////
              |
             ===
              |
             Vcc

mac

[Sparky]

Thanx for all the input...much appreciated!