Big Muff questions

[Valvehead]

I normally dont work on pedals , but was asked to look at this black Big Muff made by EH .

I think i have the right schematic. I havent had time to look at it but I was told "some guy modded it and i hate it " (wonderfull...)

After pulling my hair out ...Can anyone tell me what transistors should be in this ? this doesnt have an AC jack.

also, what is this fader on the side ????? dont see it on the scem .

[DrGonz78]

Yeah that fader threw me off completely. Maybe a blend of the two clipping stages? I have this same pedal and I can open it up to see what’s in it. However I think BC549C is what I found on a search on a reverb page. I can open it up in the morning tomorrow if needed.

[DrGonz78]

Scroll down to version 7c and 8. BC549C, BC547 and KT3102EM.

[DrGonz78]

I guess BC239C is the same as 3102EM.

[Helmholtz]

This might be helpful:
https://www.electrosmash.com/big-muff-pi-analysis

[Mark Hammer]

AFAIC, "accuracy" is moot. Most of the legend about this or that issue of Big Muff seems to regularly be based on a single example, resulting in inferences about this issue being more/less <insert quality here> than that issue. You never see anyone take 10 examples of this issue and compare them against 10 examples of that issue, in order to identify what is consistently different between them. Admittedly, that is hard to do when it comes to much older pedals.

In an interview with a business magazine about 15-18 years back, Mike Matthews said that one could take any 4 consecutive Big Muffs off the assembly line in the late '70s and early '80s and they would all sound different from each other. Truth be told, he kept production costs low by using what appeared to be a lot of surplus parts. Not that they were somehow "lesser quality". Rather, you buy a bunch of caps from this source, and a bunch from that source, and between batch differences and component tolerances the cap values are allover the place. And NOBODY was hand-selecting or matching cap values in those days, or even well into the '90s.

So major sonic differences between units were likely to be cap values and the emitter resistor values needed to goose the gain of the transistors. The nominal cap and resistor values in the tonestack also changed across issues.

I have absolutely no idea what the side-mounted slider pot might be for. If you could tell us what it seems to be connected to, and what its value is, I could probably provide some insight into what it was at least supposed to do. I'm no electronics engineer, but I've built and/or modded a dozen of these, so I have some sense of what does what.

[Valvehead]

Thanks !!!