Slurpee schematic and mods

[taeagan]

I'm looking at the Slurpee schematic and mods and I have some questions about the differences from the stock circuit. I'll list out all of the differences that I spotted - the firest few I think I understand, the others not so much...

1) R1 is just a pull down resistor not in the stock circuit
2) the led and r25 are just the indicator
3) d2, r26, and c15 are just enhancements or upgrades to the power supply to modernize it (as is the increase of c14 from 10uf to 100uf).
4) c3 is specified as tantalum in the Slurpee - any particular reason?
5) the attack, decay, bass, and treble pots (and additional series resistors associated with them) are mods
6) d1 is 1n914 in the slurpee as opposed to the stock 1n4148? Any reason?
7) d3 and d4 seem to be related to the Mark Hammer mods, although he didn't specify 1n4001 diodes. Why these diodes? And why not the additional change in the resistor value that he recommended?
c5 is 47n stock and 220n in the slurpee. Is this for more low end response?
9) c8 and r14 are 220n and 220k in the slurpee but 1uf and 47k stock. Is 1uf overkill in the stock version?
10) lastly, why is r9 in the slurpee circuit? There's no such resistor in the stock circuit. Does this have something to do with the bass/treble mod?

[midwayfair]

1. Funny thing, R1 is probably actually in the stock pedal but not represented on other circuits. EHX sometimes solders pull-down resistors to the jacks (meaning, they're in the line all the time). I had three EHX pedals like that from the late 2000s.
2. Correct.
3. Correct, but D2 is sort of a typo. It should be a 1N4001 if you are going to include it. A 5817 won't necessarily be a problem there, especially not when we're using 9V supplies, but I'm pretty sure it was an oversight on Brian's part. He may have even intended it to be converted to a series diode for better protection.
4. Size, most likely. A 470nF would typically be about twice as big.
5. The bass/treble pots are sort of an adaption from the original's switch implemented in very different way. One interesting thing about the attack control is that because the hold cap (C4) is smaller, the minimum attack setting, despite having the same resistance (100R), is half as many milliseconds.
6. They're the same diode for all intents and purposes here.
7. I'll let Brian answer that one.
8. I don't see C5 in the original schematic, but we might be looking at different things ...
9. Yes, the original was overkill. The cutoff in Brian's is already below human hearing and uses a film cap instead of an electrolytic.
10. Q1 is also not in the original. It's a buffer for the output (rectified) voltage so that it can be applied to the base of two transistors (and to the tone controls) without loading the output of the rectifier circuit and losing control voltage. The resistor is just some separation between the two following circuits. The tone controls complete the connection to ground as the buffer's emitter resistors.