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If you have the same parts with the same values, and the same opamps, then this "dark sound" will be about bad parts in one of them, in tone circuits. Here is question, which of them has that proper sound? That with dark tone, and then we must focus at that second to find wrong part. Or thise dark tone is bad?

Do you mean this one? And is it one which has darker tone than that another? What is that second device type? The same?

If everything is ok, there will be Vcc/2 (plus minus). At output pin 1 surely, at - input too. Maybe at + input will be little less. If you power is 9V, there will be cca 4,5V.

Great work! I mean such a Photoshop skills!

No. Q3 is at 4,5V. Q2 let as it is - 1,2V. That's ok. (Some those circuits even let resistor at Q2 cellector without setting trimmer, just fast resistor, only setting 4,5V at Q3. As that tonebender MK 3 as I attached.)

Great work! Now only tuning: Try biasing Q2 and especially Q3 too. But now set that 4,5 or better 4,8 V only at Q3 collector. Trimmer Q3 bias try at half setting, and play with Q2 bias trimmer - gating. (In tonebender III that I attached you can see even another resitors around Q2 and Q3. You can try them in your device.)

For a better fun I attached schemas of Suck fuzz - improved Tonebender, where you can play with many settings at breadbord. One for npn and one for pnp transistors. You can rebuild that your machine in to a Hell of fuzz :@)

That link will help. Some tips:

Ub/2 is one half of power supply. Sorry not to be clear. Picture in first post is one solution, and another picture Tonebender III is another. Try both of them and you will see what you get. Both of them will work. Here is another kind of bias setting:

http://www.hawestv.com/transistorize/germanium1.htm

All will work with proper resistors, you must find. Use trimmer and try to set cca 4,5V at collector of Q1 (for 9V power.) Then substitute with resistor with closest value.

That's I wanted to attach now :@(  Another version.

First transistor hasn't bias from plus pole to basis! I would put here cca 680-820k resistor. Set with this resistor cca Ub/2 at collector of Q1. That's for a start.

There are more versions of "tonebender", which one do you have? Any schematics? Generally try with audioprobe track signal from very start. Biassing resistors in basis of first transistor. Try to fiddle about resistor basis-ground. Change values.

I meant it this way.

Those caps you sent link, are fully sufficient :@)

At real you don't need to care about size of caps too much, if you will cucceed to get them in pcb :@) 5mm or 10mm...
Here is important value (here 100nF/minimally at 16V, if we talk about that one in power section.) Generally, for power blocking are more suitable ceramic ones. But here it will be not so important I guess. Power supply is 9V, so every cap for min. 16V will be ok at all positions. Ceramic or film... Only C2 100pF is at hi-gain feedback, so I would use film her - not too microphonic.

Maybe play around R41-R42 ratio, or put here trimmer 15k instead of them and tune proper threshold? If basic gain here is big enough (2,45), maybe this tuning can help a little.

BF245B has Ugs very similar to 5457.