FF type circuit

[Gus]

http://www.diystompboxes.com/pedals/gusFuzzFace.gif

Not hand drawn and has been here for years.

This should allow most small signal transistors to drop in and work does not need to be 2n3904s can be 2n2222as or even a mix of numbers.  It has a open loop gain control of Q1 with the 100 ohm emitter and 10K collector for both open loop control and working the transistor at a more defined Ic.  2nd stage has the lowpass filter you can also check dates for the emitter resistor and filter on the 3 tran and rocket schematics.  It also has a different way of adjusting bias, I think a better way.  If one looks close you can see a good part of an old vox circuit in it.

adjust input and output caps to taste the ones on the schematic are a starting point

Anyone build this?

[earthtonesaudio]

Reminds me of this: http://www.geocities.com/tpe123/folkurban/fuzz/fuzzyfaces.html  but a slightly different way of doing it.  I think I built this years ago but fuzzes rarely go beyond the breadboard for me.

[John Lyons]

I have built that one, Sounds great! I switch between a large
and small input caps for different "feel".

Thanks for posting this way back.

john

[brett]

Hi
I'm no expert and my memory is bad, but I think we've discussed this or similar circuits before.  Maybe in the days before the Axis Face was put forward. 

Most people seem to agree that the bypass cap on Q2 is an excellent thing for controlling harshness.  The 47k feedback resistor always seem to work a treat on Si FuzzFace circuits.

The emitter resistor on Q1 is undesirable in my opinion*  But that resistor can be eliminated and input impedance kept low if Q1 has low hFE (50 to 90).  2 "piggybacked" devices or a power device will do the trick.

cheers

*  If the resistor on the emitter of Q1 isn't tens of ohms (or more), then the gain of Q1 is excessive if it is a typical modern small signal BJT.  However, if this resistor IS more than a few ohms, the input impedance is high (>30 kohms) and the characteristic FuzzFace "bloom and sustain" effect is lost.  Also, Q1 becomes more conventionally biased.  In a Ge FuzzFace the base of Q1 is only at 0.3V and its output is very asymetric.  With an Si transistor the base is at 0.7V, even with no emitter resistor.  Add an emitter resistor and the voltage goes up further and the gain goes down - not good for asymetric ("tubish") fuzz.

[Gus]

I wonder why the piggyback threads stopped?  That was and is a cool refinement.

  I agree with the 100ohm it is not a "true" FF: However being different and sounding good is not a bad thing.  Some don't like the "Ge sound" and when it comes to taste people like different things and that is a good thing.

[earthtonesaudio]

I could be mistaken, but I thought that even if the base of Q1 had infinite impedance, the circuit's input impedance would be 1/2 of  the 47k feedback resistance.

[mattumbi]

Gus,  I've used this circuit recently and compared it side by side with a germanium ff build. I could achieve very similar tones with both units by a little knob turning. Thanks.

[petemoore]

  Easy enough to switch by the Q1 emitter resistor [100ohm?].
  Picke the value right and that switch might make "1 hard choice = two easy's"...a gain boost.