That first gain stage in the Zvex fuzz factory -- how does it work?

[mordechai]

I was comparing the first gain stage in the FF with the first gain stage in a tonebender Mk II.  The FF obviously lacks the 100K to ground before the base of Q1, and incorporates the 220K across the collector and base.  But given that the rest of each circuit so closely resembles a fuzz face, the difference in tone caused by the changes in this first gain stage is amazing.  Clearly, using a silicon transistor as opposed to a germanium in Q1 makes a difference, but I've heard Tonebenders with a silicon Q1 and it's still a tremendous difference.  Can someone explain what the lack of the 100K to ground and the addition of the 220K across the C/B of Q1 is actually doing that changes things so dramatically?

[Gus]

Search for transistor biasing on the web or in a book.   Note input resistance, gain and temperature stability of each type of biasing.

[Toney]

Perhaps have a look at the LPB1.
Its the simplest of transistor boosters and getting familiar with biasing will help lot. You can just breadboard it, if you have one, replace the resistors with pots and fiddle away.

[Gus]

Found a screenshot of a DC operating points sim I did to show how the C to B resistor interacts with the transistor used with the circuit that use a C to B transistor like in the screenshot.  IIRC I used one of the electra distortion schematics for the values in the sim.

[kodiakklub]

sorry, but, LPB1? which pedal is that? i myself need to learn up on transistor knowledge.

[artifus]

http://beavisaudio.com/bboard/projects/bbp_LPB1.pdf

http://beavisaudio.com/techpages/HIW/hiw1.gif

[mordechai]

Found a screenshot of a DC operating points sim I did to show how the C to B resistor interacts with the transistor used with the circuit that use a C to B transistor like in the screenshot.  IIRC I used one of the electra distortion schematics for the values in the sim.

Thanks Gus.  I can se that the bigger the resistor, the greater the change in voltage, and I can imagine that this would impact the tone significantly.  What I am not clear on, though, is how this differs (though I know it must) from the setup in the LPB, where the resistor going to the base of the transistor is also going to the power rail and has its 'parallel' resistor going from the base to ground.  The other question I have is related, namely, what happens if the 100K resistor connected from the base of Q1 to ground in the Tonebender Mk II is added in front of the transistor in the screenshot you posted?  Would that "steal" some of what is feeding the transistor from the C to B resistor you posted?

[LucifersTrip]

I was comparing the first gain stage in the FF with the first gain stage in a tonebender Mk II.
But given that the rest of each circuit so closely resembles a fuzz face, the difference in tone caused by the changes in this first gain stage is amazing.

The Factory is a Fuzz Face variant with an extra stage and loads of controls....and a TB MK II is also a Fuzz Face with an extra stage... so the real question is, What makes a TB MK II or Fuzz Factory so different than a Fuzz Face...

The big difference on the Fuzz Factory, of course, are all the controls, but it can get Fuzz Face tones...It's the TB MKII that is really different, and I think a large factor is the biasing. Remember, the Fuzz Face has Q2C set at around 4.5v, but Q3C on the TB MKII is set at 7-8v+