Temperature Stabilizing Diode In Germanium Circuits

[SpaceCommandant]

I'm curious if anyone has any insights about the use of diodes in circuits that use germanium transistors. I've seen a couple that utilize a diode from emitter to base to keep the tranny in the sweet spot, but I'm wondering what other germanium circuits would (or wouldn't) benefit from this

[Silver Blues]

I had this discussion with someone somewhere for sure. I think this began with the Fuzz Face, someone stuck a diode in there as you describe to correct the temperature-induced bias drift and it seemed to work nicely. Not certain anyone knows how it actually works, I have a theory that may or may not (probably not because I'm not an engineer lol) be correct though. The way I've always thought about it is that a germanium diode also has similar drifting of forward voltage with temperature, and tying the base to ground with the diode lifts the base one diode drop; since the diode will drift in tandem with the transistor, it compensates for the differences. Kind of the way an NMR spectrometer corrects for magnetic field drift by tracking deuterium resonances simultaneously to the nucleus you're probing, if anyone knows anything about that.

That's just speculation though, take it with a grain of salt. Nevertheless an interesting property of the system, and I think that most any germanium circuit would benefit from it so long as the tone isn't changed (or maybe that's what you want!).

[Travis]

It's called reverse biasing. It probably began in an electronics textbook but the earliest guitar effect that I can think of that employs it is the ToneBender MKIII/MKIV