Big Muff Pi (Op Amp Version)

by gaussmarkov

Big Muff Pi (Op Amp Version)

Chris Gregory <> suggested this one. He also verified it and helped improve the layout. His build is pictured. Paul Nelson authored the source schematic:

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20 Responses to “Big Muff Pi (Op Amp Version)”

  1. culturejam said:

    I just built this tonight. I really dig the sound. But I accidentally swapped the volume and sustain pots, so it’s quiet with some insane wooly fuzz when dimed. I love happy mistakes.

    Thanks for making such great layouts! 🙂

    Posted 02.09.2008 at 6:39 pm

  2. dooby doo said:

    hi any chance of anyone building a distortion along the lines of an mxr dd11 dimebag style pedal…for massive gain and crunch…

    it would be a brilliant project…

    Posted 22.02.2009 at 8:25 pm

  3. edvard said:

    Holy smokes, that’s tiny!!

    I fixed a friend’s op-amp BMP years ago and the circuit took up the entire case. Those things were like 6″ x 7″ or so…
    Nice work!

    Posted 16.07.2009 at 4:58 pm

  4. prima said:

    What a great circuit, this is real man…awesome. Thanks

    Posted 23.12.2009 at 2:11 am

  5. Tony said:

    Had a bit of trouble finding the out as it isn’t marked or noted in the schematic or pdf. I went to the original site (Paul Nelson) and he had it marked hehehe

    Thanks for the layout!

    Posted 15.01.2010 at 4:13 am

  6. Nick Dunkerley said:

    My first build for 15 years! Bar a couple of sloppy wiring errors,worked straight off.Sounds monstrous!! Also,cost very little ,used recycled box,switch,jacks,pots! I am a happy man!! Thanks millions,I WILL be building more!

    Posted 25.03.2010 at 6:45 pm

  7. David said:

    I made it, few months ago! an awesome pedal closer to the SP sound on Siames Dream!!!

    Posted 20.04.2010 at 3:04 pm

  8. Conner said:

    are the pots lin, log or audio?

    Posted 14.06.2010 at 10:58 am

  9. Old Fat Bubba said:

    The sustain and volume pots are log while the tone is linear, I believe.

    Posted 26.06.2010 at 7:13 am

  10. Mike said:

    Does anyone know if there is a way to buy PCBs so I don’t have to etch my own? Thanks.

    Posted 30.06.2010 at 6:29 pm

  11. JoeSixString said:

    On this site, see Using a Fab House.

    Posted 01.07.2010 at 12:28 am

  12. Mike said:

    Thanks, Joe. I also found this site which is selling them completely fabbed:


    Posted 01.07.2010 at 7:47 pm

  13. Metalbox said:

    Need some mods for use with bass?

    Posted 16.08.2010 at 12:57 pm

  14. Big Muff Pi | Mechinations said:

    […] some dirty, dirty grit into my guitar sound. The circuit for such a thing is readily available on, which means all the hard work is already done, and you can enjoy building a sweet box of tone! The […]

    Posted 14.02.2012 at 10:48 pm

  15. said:

    I could find a 200uF capacitor… I believe it is used as a low pass filter R14, C10 filtering at 16.9Hz… So is it possible for me using a 220uF capacitor with 43 Ohm resistor, also filtering at 16.9Hz ?

    Posted 16.02.2012 at 7:43 am

  16. Dale said:

    Will a UA741 work instead of LM741?
    Is the UA just a manufactures id?

    Posted 06.04.2013 at 8:31 am

  17. Juergen said:

    Where would I put a LED to indicate the active pedal into the circuit? Also I can’t find the LM741 at taydaelectronics, with what IC would I best replace it?

    Posted 07.08.2013 at 8:46 am

  18. gm said:


    Directions for wiring in an LED are in “Wiring Up a 1590B” on this site. You can get the LM741 from Small Bear Electronics (


    Posted 09.08.2013 at 12:14 pm

  19. miku said:

    Heya great stuff
    I have a few other effects circuits plugged in too, however this one has a much lower volume than the others, maybe I botched it somewhere, it sounds great though. Can I do something like increase or remove r13 to make it louder.
    or should I make an amplifier for the output.
    Does anyone else notice it as quieter than other effects, perhaps its just a quirk from my assembly.

    Posted 22.02.2014 at 10:21 am

  20. miku said:

    Ok in the excitement I have put 0.1uF where there are meant to be 1uF, will update when I manage to get some and rebuild it.

    Posted 06.03.2014 at 9:40 pm