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By choosing the correct caps, you get the same effect. Whether you parallel 2 caps or 3 to get 4+uF, it doesn't matter. The electrons don't care. I'll spell it out for you: C5 = 470nF Ca = 1.5uF Cb = 3.3uF C5 + Ca = 1.97uF C5 + Cb = 3.77uF that should be plenty close. If it's not, then use...

Ya beat me to it! It will pop when switching. To cure that put a 1M resistor from pin 1 to 2 on the toggle switch and another from pin 2 to 3. I recommend film or tantalum caps.

Indeed. It was a ticking time bomb that might never have gone off. Or it could have killed me while hiking over an 11,000 foot pass in the Sierras.

Yup. About a year ago to fix an Anomalous Origin of the Right Coronary Artery. Had it all my life without knowing it because everything was working ok. They spotted it on a CT scan when they were looking for something else. Fixing it was a preventative measure.

Since we're sharing scars...

Not good, should be equal to Vref. Oh, now I see it. You have pins 2 & 3 swapped on U1. It's a wonder any sound comes thru at all. TONE & LEVEL are also wired backwards. This you first board layout project?

You have Q1-Q4 D & G swapped in your measurements. The DMM is slightly loading the measurements at Q1-G, Q2-G & Q7-B, but we can correct for that. Looks like there is flux reside on the board. If so, clean that off. Your schematic has Q5 E&C swapped. Same for Q6. The datasheet is 100%...

OK guys, please take it somewhere else. Start a new thread in General Questions. You can link to discussions here, but I'm try to keep the thread short and to the point.

Are the readings for the JFETs D-S-G? Are the readings for the BJTs E-B-C? Complete information is good. Q1-S & Q3-S are connected together. Why are their voltages different? Same goes for Q2 & Q4. Q5-C and Q3-G should be the same voltage because Q3's gate current is essentially zero. 3...

Why do I feel like this discussion has drifted from the topic of how passive filters work to design mods for the Chickenhead?

3.9M should be close enough.

I wouldn't expect all of the resistor values to be the same if Q3 is changed to Germanium, but I've been wrong before. Check the collector to base voltage on Q2 because it will be much lower than if Q3 is Si.

IMHO, transistor sockets in pedals is no bueno. It's a potential reliability problem. If you must use sockets to select transistors, which BTW is not necessary with the Aldrin, then after selecting transistors, either remove the sockets or solder the transistors into the sockets.

The drain voltages on Q1 & Q2 should be about 8.4V because Q5-B and Q6-B should be Vcc - Vbe. Q5-C and Q6-C should be close to Vref. Make sure the 2SK193s are oriented correctly, Did you test them before installing? Make sure Q6 is 2N5087 and that it is making good contact in the socket...

What are your favorite new production EL84's? I'm replacing the output tubes in a Monoprice 15W amp that a friend gave me. One of the JJs in there has become gassy and lights up like the 4th of July.

We can do a quick cocktail napkin calculation to get into the ballpark. Maximum output swing is around 8Vp-p. Assuming a square wave, that works out to 4Vrms. There is a 560Ω series resistor (R15). Output power is Pout = 4^2/560 = 29mW delivered to R15. This is pretty much the worst case...

Depends on how much volume reduction you're looking for. Start with 220K and adjust from there.

This one's done. I tried some clipping options on the 1st stage just for S&G, but there were no improvements to be had.

Or move to Canada.

I had a little help from Claude.