I agree that modding Old Big Muffs is becoming a thing of the past, as original good ones are getting too expensive and thin on the ground, but...
When you get your BR back in your hot mitts you could open it up,
How to Disassemble a Vintage Big Muff , and measure all the component tolerances and make a clone that you wouldn't worry about destroying through
modding.
Caveat emptor, there are errors in some schematics, or EHX subbed a part on a particular day/week/month/year that's unlike that particular Muff model...
For mods, from what I've researched the EHX OG Russians already have the best clipping caps of all the Muffs (47n), I think this is what makes the Green, Tall Font, Black so special on bass — from what I've read, all
very theoretical. Very.
Other mods you could do may improve bass, but at a cost of crunch, making the Muff a smoother less-aggressive fuzz. It's a real push-me-pull-you circuit. I'm in my second-wave of obsessing over this circuit and currently have drawn up two schematics for Muffy ideas I want to try, and in a few minutes I'll be drawing up two more... so this thread is rather fortuitously timed for me.
I've been down the
Kit Rae Rabbit Hole many times, and it just goes deeper. The way it's organised though... you find something once and it's hard to find it a second time, so you have to explore the warren all over again, for things like this:
I'd try increasing feedback caps C10, C12 and C11 to 500pF or 560pF. Some Ram's came with 680p for C11 and C12.
Another thing I'd like to try is increasing all coupling caps — C1, C4, C5, C13, C3 and C2 — to 220n (they're all 100n). It'll be more bassy, but will that make it fart out? Other Muffs have all couplers as big as 1u, and some have in/out caps of 10u, yet aren't considered great for bass (which I think is because the clipping caps C6 and C7 are correspondingly huge, too).
So after enlarging all those caps, the circuit will lose some of its bite, so I understand. To counter mush, I'd then decrease the emitter resistors (390 Ohms) in the clipping stages to 330r, 220r or even as low as 100r — could even try ditching them altogether, but at what point is it no longer a Rusky? Does it even matter if it's a clone and you're getting the sound you want?
Could also lower R12 and R19 limiting resistors from 10k to 8k2 or 7k5 to get back some gain and grind.
The clipping caps are the key, I think. Larger they are, the more range of the signal gets compressed through clipping; compressing the lows diminishes their perceived volume. By using small caps, you clip only the higher frequencies and so the low end is less compressed, so even though the couplers are only 100n and not bigger "bassier" values, you still get good bottom-end when the sound leaks from the output jack.
Theoretically.
The circuit guide also suggests for the collector resistors to reduce gain for a more controlled clipping — whatever that means... No idea, and like a eunuch in a brothel I'm unable to do anything 'cause I've had to pack away all my equipment, I can't test these ideas in the physical world until late spring, maybe mid-summer...
Search the Web for other bass-intensive mods: Premier Guitar, Wampler, Nicholas Kula's article in Tone Report 90 (now found at Reverb dawtcawm, maybe), Electrosmash's analysis, Coda Effects, Zorg... etc.
Sorry, no time to give you all those links, I've got Muff schematics to get back to tinkering with...
