What's the diode in the 3 knob tonebenders purpose?

[marrstians]

does it just set the bias to Q3 or does it add distortion like alot of other types of circuits? would there be any benifit to using different diodes, or more diodes, so it might produce  more even harmonics? i'm not really sure...

[phillip]

Since it's reverse biased, I think its main purpose is to help Q3 maintain its bias when/if the device starts to heat up.  Since the 3-knob ToneBender was all Germanium, it would've suffered from temperature instability problems like the Fuzz Face and ToneBender MKII (and other similar designs), and that reverse biased Germanium diode would help to minimize that problem.

Phillip