First PCB Layout of 2006. The 1977 Opamp Big Muff.

[nelson]

I built it adding a jumper on the 220k resistor. I'll post the correct version as soon as possible.
It works very well and it seems way less noisy than the transistor version!
There are a couple of other considerations about this project: Paul, check your mailbox.

Already done, check yours.

[Zero the hero]

   Checked!   

Corrected PDFs are online!

[nelson]

Here are some pics.

[NoFi]

Nice work !
I have an original from 78, there are a few circuit bendings tricks.
I inserted wires from around the 62k resistor (pin 6 of the op amp) to pin 1 of the same op amp and/or to lug 1 of the sustain pot, and it does a few "FuzzFactory-like" feedbacks and synth like sounds. I also replaced the 8.2k resistor by a pot (lots of noise).
But apart from that, the pedal is a one trick pony. I tried using various Leds, trimpots etc. to expand the versatility and try to get it to overdrive nicely. That was a failure. So i cannibalized it. 



Well, not so original now i guess. 
While "experimenting" i also noticed a strange thing, the pedal distorts like crazy even without the clipping diodes/LEDS (hence the switches lol).
The clippng diodes only seem to be there to smooth out the distortion. I'd like to found out how to balance the Op amp distortion and the clipping diode saturation. The op amp distortion is probably what makes the tone thick and muffy, i'd like to be able to get rid of it.
On mine, with the sustain knob backed out, the pedal basically craps out and yeilds a very bassy and nasty, crackly and muffy drive, not very usable.
Is it the same with yours ?
It would be great to try and make the OA big muff better and more transparent in the low gain zone. The transistor muff is better in that respect.

[mrsage]

Very cool!

I would totally build this if I didn't already have a Euthymia ICBM fuzz (which I completely love).

Then again, I may build this anyway because I can't quite seem to get enough of the muff!