ESR Graphic Fuzz | I'm going mad

[jessenator]

So I breadboarded one based off of the original schematic I found over at DIYSB
https://www.diystompboxes.com/smfforum/index.php?PHPSESSID=0v448fu3gilak3iocmca8ddam1&topic=83300.msg1212719#msg1212719
It worked! It's crazy unruly, but I like it. I read up how since it does split-rail power, and grounds to your instrument/amp sleeve connections.

So I found FuzzDog's version updated to work along the same lines, but will take more normalized 9V power and play nicer with pedal boards.

I've tried to breadboard this bloody thing about 10 times, and I'm going mad. I can't get it to work at all. No signal. I have a screenshot of that schematic with some highlights and such. I've marked what I think the outlined nets are providing, but I'm still not getting anything.


http://pedalparts.co.uk/docs/GraphicFuzz.pdf


Can this thing run on brick power at all (fuzz, or does it only work with a 9V cell? (I tried both, but nothing) I mean, I'm sure the fault is on my end, but I'm hot and bothered by this thing.

Is this somewhat of a tilting at windmills and I should spend precious hours of life on other projects?  : P

[mauman]

That bottom rail is indeed ground, and should be connected to your DC power negative terminal as well as the output jack shield, which will provide your floating DC with an earth ground from the amp.  All the connections look right, and component values look reasonable.  Your volume pot arrangement will present a variable impedance to the op amp, usually lug 3 is toward the op amp and lug 2 toward the output, but it will work as-is.

[jessenator]

That bottom rail is indeed ground, and should be connected to your DC power negative terminal as well as the output jack shield, which will provide your floating DC with an earth ground from the amp.  All the connections look right, and component values look reasonable.  Your volume pot arrangement will present a variable impedance to the op amp, usually lug 3 is toward the op amp and lug 2 toward the output, but it will work as-is.

Thanks! Well I went back and checked all the connections again and I forgot to ground the portion of the voltage divider! durr

Well now it works! It's much noisier than the battery version (I even did a 1N5817 in-line with the +9V along with other power filtering stuff before the divider). This is even with lars' mod of putting a 10k trimmer between pins 1 and 5 of the 741 :S

Tuning it just so, and cranking the 1M filter pot barely contained the noise, but I found that if I removed the filter pot and popped a 2M2 resistor in its place, it's instantly tame.

Actually playing it a bit more and putting a Bosstone in front of it, I didn't really need the trimmer, but that's a bog standard 741 chip in it.

Apologies for the camera bumping (it was making noise sitting right on top of the input jack on the desktop.

It's overly bassy (no surprise there), but I don't mind it. Needs some tinkering, but thanks, mauman, for remotely spooking my breadboard into cooperating 

edit: also excuse my playing—I've never sat down and tried to play that song, and I'm super rusty as it is.

[jessenator]

Forgot one thing: I looked at the RJV schematic post today and noticed it had one change compared to my previous battery breadboard: a 10k resistor in series before the volume pot