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Nothing to do with music or electronics, just some interesting mechanical stuff.

Can you explain the clear & diffuse red LEDs?

My pedal name generator has conjured these up: Vintage Soul Wizard Sweet Germanium Hammer

Turns out the pedal name "Germ Warfare" has been taken. Let the naming begin.

Two things: 1. Low-leakage NPN germanium transistors are not easy to come by. R7 can be used to adjust the bias on Q2, and I added (optional) R21 so that Q1's bias can be tweaked if necessary. This mod works on v0.5 and v0.6. 2. Q3 does not have to be a JFET, a MOSFET will also work. I...

Q1 measures Iceo= 120μA. Q2 measures Iceo = 260μA. These are goals, not requirements. R3 & R6 can be adjusted to dial-in the collector voltage. If you remove R3 or R6 and the collector voltage is below 4V, then the transistor is too leaky.

Good catch. Schematic corrected.

First time I've seen one. I may use it in some other circuits.

Do they put in fake LM308s?

Phill in Perth sent me a link to the Box of Germanium layout. It's basically a Zvex Box of Rocks with the MOSFETs replaced by low-leakage Ge transistors. A clever idea. I wasn't happy with the biasing and a few other things, so took the basic idea and ran with it. This is the current...

It's ok to tweak the resistor values once you get close.

That's correct. I don't design PCBs. There are guys here who are very good at it, so I defer to the experts. ;)

I use J201's for Q2 & Q4 in the breadboard build of the version shown in the schematic in post #22. The DC voltages shown are consistent with J201 measured specs. The particular devices I used required the R9 & R15 values shown. If I used different J201's, it is likely that I would have has...

Don's cool, I can cut him some slack. :cool:

It can, depending on the downstream load. The input impedance of an emitter follower is approx Zin = β * Re. With a 10K load and HFE = 200, the input impedance is 200 * 10K = 2Meg. If we want even higher Zin, then a Darlington, JFET or opamp can make Zin = 100M or more. At that point, the...

This thread is about the JFET, but I'll answer your question here. The Fuchsia is very forgiving re: Q3 specs. Just about any NPN Ge tranny will work. I'd look for HFE between 50 and 100, just an educated guess. When you say: "...really low gain germanium’s..." how low are we talking about?

Replacing the pull-down resistor is not about improving the gain of an emitter follower, it's about improving the linearity and output swing. Imagine the usual emitter-follower circuit where R4 & Q3 are gone and Q2 is replaced with a 10K resistor to -Vcc. The gain is still extremely close to...

Yes.

Let's make sure we're on the same page. When I was talking about freq response, it was in reference to the KG389. Since the KG389 is not a buffer, we'll stop talking about the KG389. Unless R2 is very large, somewhere in excess of 100K, it will not affect the freq response in this circuit: