This is a library of perfboard and single-sided PCB effect layouts for guitar and bass. I'm not an electrical engineer by any stretch of the imagination, just a DIY'er who likes drawing layouts. It is meant for the hobbyist (so commercial use of any of these layout is not allowed without permission) and as a way to give back to the online DIY community.

Tuesday, February 17, 2015

Electro Harmonix '77 OpAmp Big Muff

In the late 70s, Mike Matthews and EHX took the Big Muff on a detour from the traditional 4 transistor circuit in favor an IC-based circuit. It sounds very similar to the traditional Muffs, with the tone control being a little more flat than the traditional mid scoop. The circuit uses two favorite opamps from the 70s–the JRC4558 (used in the Ibanez Tube Screamer) and the LM741 (used in the Distortion +/OD250). The IC Big Muff would have probably faded into the background of Big Muff lore if it weren't for Smashing Pumpkins guitarist/frontman Billy Corgan. His use of a late 70s IC Muff on Siamese Dream has made the pedal highly sought after.

I've drawn the layout to use right angle pcb mount pots, mounted on the solder-side of the board. Also, if 741 chips aren't to your liking, you can use something like a TL071 in its place. Just increase the 820k resistor between the power and pin 3 to 1M.

21 comments:

  1. So tried this one yesterday and I'm getting weird self oscillation/ whine/ sound... (over the top of a dull/quite distorted signal).
    Nothing obviously wrong and can't find any signal without the sound with a probe. It might be something I've done... will have to take off the pots and get serious, unless you have any pointers.
    I'll keep you posted.

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    1. Hello, this is the solution...
      http://www.subeimagenes.com/img/12369763-1037737392923332-2114593708-o-1595407.jpg

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    2. Whats the solution bro? I can't see the image anymore

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  2. Big Muff 77 OpAmp verified from Mendoza Argentina ...thanks for your work...
    http://www.subeimagenes.com/img/12369763-1037737392923332-2114593708-o-1595407.jpg
    http://www.subeimagenes.com/img/12367042-1037737572923314-193364252-n-1595414.jpg

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  3. Verified mate!!
    Just change the 150pf ceramic caps value to 16pf and we will get that siamese dream sound.
    Thanks mate.

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  4. I have done. It works perfect.
    Thanks for the scheme

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  5. HI!

    In my build tone knob doesn´t seem to be working, i can hardly notice any change when i roll it

    Any ideas of what´s happenning?

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    Replies
    1. My guess is you've got either a wrong value somewhere in the tone stack or just a bad component.

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  6. Hi all, I built this effect but get no output whatsoever. Upon improvised tracing of the signal (a wire with a cap held to the effect) I get:
    At IC1 (4558): Pin 1 (output stage 1) has good signal. Pin 5 (input stage 2) has about the same volume as pin 1 but is more muffled sounding (high frequencies lost somewhere?). Pin 7 (output stage 2) has a oscillating high pitched noise with only a little of the original signal in the background. What I tried so far: put a different 4558 in there. There was no change. What could be the problem here? Thanks in advance, Hans

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  8. Hello I tried this project, but I have a problem, like this...
    ""4, 2016 at 1:49 AM
    So tried this one yesterday and I'm getting weird self oscillation/ whine/ sound... (over the top of a dull/quite distorted signal).
    Nothing obviously wrong and can't find any signal without the sound with a probe. It might be something I've done... will have to take off the pots and get serious, unless you have any pointers.
    I'll keep you posted.""

    I know there ate a solución, but I don't know what is... Can anybody help me?

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  9. Can I use a LM4558 instead of a JRC4558?

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  11. Hi, could somebody please share the schematic used for this layout? I thought the opamp version had a tone switch.

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    1. The '78 had the tone switch. Here's the schem for the '77:

      http://4.bp.blogspot.com/-uPihslDUHDQ/T-_KYkCwr8I/AAAAAAAABdI/-r-Fw359liA/s1600/EH_BigMuffPi_OP-77.gif

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    2. This comment has been removed by the author.

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  12. If anyone builds this and adds a tone bypass please reply and let me know how you did it. I may have it figured out but I'm not super confident.

    Sounds great as is but I would really like to try it with the mod! If you have any other cool mod suggestions I would be happy to hear them!

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  13. A big THANK YOU to everyone on this site and comment section. Built this and it works great,

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  14. can you / would you do a layout for the '78 please please please?

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