What is D1 doing in this fuzz, besides making it work better?

[midwayfair]

Or, in the words of Mr. Jimi, "What have I recreated this time?"



I can at least describe what's happening electronically: When I play a note, the voltage on the Q2 collector drops from 6-7V to about 3V (which I should expect -- the diode is doing some rectification, right?). Smaller signals drop the voltage less. I'm not sure, but I think a really big input signal would probably put Q2 into cutoff. If I use an LED, there's less distortion.

One thing I can't figure out is how the heck Q2 is working at all. I just kept removing resistors and it kept working. I assume leakage, but ... the leakage on the transistor I'm using is incredibly low, only 5uA. Normally I need twenty times that to even get Q1 in a MKII Tone Bender to "turn on."

(Incidentally, this was made just to use certain parts. That's why all the caps are the same value and the resistors are a little sparse.)

[PRR]

> the diode is doing some rectification, right?

If the diode is poled as shown, it can only pull Q2 collector *up*, not down.

> When I play a note, the voltage on the Q2 collector drops from 6-7V to about 3V

That probably happens without D1, no?

Q2 is not explicitly biased. Its idle current is super low. Signal can cause much-more current, but not-much less current. With signal, average current increases, collector voltage drops.

I would suspect that D1 prevents it from dropping "too much".

There may be other ways to do the same thing. But if it works, be happy.

[midwayfair]

> the diode is doing some rectification, right?

If the diode is poled as shown, it can only pull Q2 collector *up*, not down.

Yeah, I wrote it backwards and forgot to edit my post.

I guess I'll just have to be happy, then.

Thanks, PRR!