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Hah. I get that reference 😄

The power supply I'm pretty clear on. It looks to be taken pretty much straight from the datasheet of the TI LT1054 (Figure 22. Dual-Output Voltage Doubler) with different diodes/capacitor values. It puts out +/- 18V minus some diode drops as far as I know. Pretty damn good and very useful for a...

I wouldn't know, you're the pro :) People keep bringing this one up as a great transparent volume boost so I guess it works. I do have the board and parts here, just haven't gotten around to building it. There's more stuff I don't really understand the purpose of. The second op amp seems...

What is the purpose of R2, R3 and C2 in the input section?

It's an older revision of the ADHD https://docs.pedalpcb.com/project/archived/ADHD.v2.pdf

When you drive an op amp beyond its output swing range, 0V to 9V for example, the output signal will start to clip. More gain = more clipping. Less supply voltage = earlier clipping. You bias to 1/2 VCC, 4.5V in this case, to ensure the output can swing symmetrically around this midpoint because...

Well, vref will usually be 1/2 vcc. There's no schematic, but I'm guessing the two 1M resistors form the voltage divider that sets vref to 1/2 vcc. Change one of the resistors to another value and the reference voltage will be offset from the usual 1/2 vcc. This would allow the op amp to swing...

You could mess with the resistors in the voltage divider that establish vref but why would you? Maximum headroom and stability will be achieved by biasing to vref.

Cool project and seems to work pretty well! I've been meaning to try the AMZ Pickup Simulator for a while, which seems to be pretty much the same circuit.

I've built a couple of these over the past few months and you have to be careful with how you lay out your wiring. Running the input wire too close to some parts of the circuits can introduce crosstalk. Shielded wire helps and is a must in my opinion for the ins and outs of this circuit...

Looks very cool. I want one! A while back, I built the Aion FX Draco, which is based on the Dr. Boogey circuit, which in turn is also based on the red modern channel of the Dual Rectifier but with JFETs instead of tubes. PedalPCB also has a Dr. Boogey variant, the Boogie Monster. Anyway, while I...

Same manufacturer, slightly worse specs but it won't matter for our purposes. Seems like a good fit. There probably are other DC-DC converters by different manufacturers with specs even closer to the obsolete part available, maybe even cheaper. Would have to compare datasheets. In other words...

I'll have to look into that. I wanted to use these in NPN Rangemasters if leakage wasn't too high but that's not going to work I guess.

Not great 🥲 So yeah, avoid the AC187K at Reichelt. So they are. Guess I got some cool new GE clipping diodes now.

That's a bummer. I had an alert for some AC187K back in stock at a big German electronics store (Reichelt), so I placed an order yesterday. Not even sure where these come from. Reichelt doesn't usually deal in NOS as far as I know. Should be here tomorrow or the day after. I'll post my findings...

That is the way. The reverse image search on AliExpress is pretty good as well. Used it a number of times to find bulk deals on knobs I saw on Tayda or elsewhere.

The master volume control is a simple voltage divider. With the master volume at max, the 11K will form a voltage divider with the 10K of the master pot going to ground. The maximum achievable output volume will be dropped by a little more than half because of that.

The low pass filter is formed by the combined resistance of the filter pot and the 1.5k resistor, and the 3.3n capacitor to ground. So the cut-off frequency is 32kHz with the filter pot at minimum, and 475Hz at max. The 1k resistor is there to limit the current going to the diodes. But either...

That appears to be it. Thanks for the link!

I was experimenting with the below Rat circuit (Aion FX Helios). The mode switch is on-off-on. I took out the LEDs (D8, D9) in order to only hear the op amp clipping with the switch in the off position. Another mod was taking out the diodes D4, D6 and D7, leaving only a single 1N914 (D5)...