more results...

So I got my dual-gang pots in, and hooked up the full two-tube circuit.  And... it's better...  But still no "home run", I think.  There's a good amount of gain, for sure, and I do hear the time-varying effects that I associate with "true fuzz", as opposed to mere overdrive or simple distortion.  However, it seems like there's a lot of tweaking and adjustment to be done, to really dial this circuit in.

For one thing, the dual-gang pots are dual 250k, whereas I was using 500k and 1M pots before because that's what I had, just to get started.  But now, the one-tube mode seems to have a lot less gain than it did before.  Given the nature of the circuit, I don't quite understand how decreasing the pot values can have reduced the gain, but that's the main change I've made.  So clearly, I don't really understand how this circuit is working, vis a vis how it's *supposed* to work.

Also, as I turn the bias pot, there is a time-lag effect due to the relatively giant capacitors, as the circuit actively re-biases itself.  This is, overall, what I want, but during the lag period, any time the knob changes position, there's a brief moment of what sounds like much more gain and crunchiness, and then the circuit "tunes itself out" back to a lesser gain mode.  So the basic behaviour is in the ballpark of what I'm looking for, but it's somehow not tuned right into the peak of hotness, where I want it to be.

The very best tones are obtained when I turn up the output level and overdrive the input of the Fender Champ, on top of the two-tube fuzz.  That's nice, but it highlights the fact that the fuzz circuit alone is not yet producing what I want from it.  With two tubes in cascade, there should be an absolute excess of gain, but that's not actually the case.  There's really no interest in running the gain knob anywhere below max.

So in summary, these experiments so far do validate my concepts that the essence of fuzz tone lies in the active feedback-biasing path, and that tubes as well as transistors are capable of creating this effect.  But the specifics of my circuit are not correct yet; they give a hint of what I seek, but it remains elusive...


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