Earth Sounds Research Graphic Fuzz Schematic

[FredB]

Does anybody have a schematic for a ESR Graphic Fuzz?

[teemuk]

Google search finds hi-res photos of the entire assembly as well as from both sides of the tiny PC board. There's a single opamp, two pots, 4 resistors and 4-caps. I'm pretty sure you sketch a diagram in less than half an hour.

[FredB]

I found one, thanks.

[teemuk]

I found one, thanks.

If you refer to this...

...then I'm afraid it's full of blatant errors.

I'd still rely on sketching the circuit from the high-res photos you can find with google search.

[J M Fahey]

It's a joke, isn't it?
PLEASE post the link to that jewel of reverse engineering.
Thanks.

[FredB]

Yes, that's the one. From my examination of that circuit there is only one critical err. Remedying that, I've got the circuit as presented to work in simulation. There is another thing in that schematic that might be an err or might be by design. Today I will bread board it and see how it sounds. That should settle it.

I might trace the images anyway just for due diligence.

Thanks and best regards,

Fred

That's interesting, the images of the board do show one more resistor in the circuit than the schematic shows.

Tracing...

[J M Fahey]

Only one error?
You are too generous
The guy is a genius, with only 10 parts, he manages to have 9 errors.
Incredible.

[FredB]

Well, I successfully bread boarded the circuit today. So yes, I would maintain there is only one functionally critical err in that schematic.

I took the liberty of changing a few things to make it perform in a more well behaved manner, created a layout for it, and now just need to acquire the usual items to bring my vision of this strange little circuit to life. Stay tuned for the demo video.

[fldrvr]

Well, I successfully bread boarded the circuit today. So yes, I would maintain there is only one functionally critical err in that schematic.

I took the liberty of changing a few things to make it perform in a more well behaved manner, created a layout for it, and now just need to acquire the usual items to bring my vision of this strange little circuit to life. Stay tuned for the demo video.

Hey Guys:

Hello, this is my first post.

I've been looking for a good schematic/layout for this pedal. Can you detail what possible errors there are in the existing schematic? (i'm a noob and would not be able to figure it out).

FredB- Got more details on your build? Your layout would be greatly appreciated. Very much looking forward to comments on the original schem vs your changes. Thanks!

[FredB]

Well, if you do a Google search as was recommended to me earlier in this thread, you can find hi-res images of both sides of the circuit board to give you an idea as to the original layout of the effect.

Then some reading up on the two basic op-amp configurations, inverting and non-inverting, should help you to recognize the err in the schematic. it's a simple one.