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.

Friday, June 24, 2016

Keeley Psi Fuzz

Happy Fuzz Friday, everybody. The Psi Fuzz is an IC/germanium hybrid fuzz. It takes some inspiration from the IC Big Muff, but with Keeley's own distinct design touches. Schematic can be found here.


  1. You could make the layout of pedals barber direct drive and gain changer ? Thank you for your great job .

  2. You can verify this effect. I built it and it works. I used 2N1306 for the transistor as that's all I had in stock. Sounds brilliant. Thank you, great site.

  3. I just finished my build using the pcb. I still had two ac187's left from another project and this seemed like a good destination for one of 'm.
    It's certainly it's own beast. A very versatile fuzz. I added a switch with a few capacitors on the input in addition to the stock values. Within a 1-10nf value it tightens up to distortion like territory.
    A very cool thingy.
    Thanks for another inspiring project!
    I love your site

  4. What kind of capacitors are 1uf ones?

  5. Got a really heavy distorted sound out of this circuit. Built a second one but it sounds the same. Too much distortion or fuzz, cant regulate it down to a creamy sound, what could be the problem? Using 3mm red led's, polarity is unimportend? Any ideas? Thanks in advance.

    1. I replaced IC's, diode, Transistors, checked all values, but no improvement. After checking the schematic i noticed some differences.
      The bridge from Pin 1 to 10 in the schematic is from 1 to 13 in your build. The 3,3k resistor is not connected with pin 9, and there is even more. I´m not that specialist like you`re and really love your work here, but this curcuit is driving me crazy because i want it to work.

    2. The IC pins differ from the schematic but it will work the same. A quad IC like the TL074 has 4 individual op amps built into it. They all work the same, so what portion of the circuit goes to which pins doesn't matter as long as they're feeding into the op amps correctly. So don't get hung up on that. Check out a pinout image of a TL074 and you'll see what I'm talking about.

      Not sure what the issue is with your build unfortunately. The layout has been verified, so double check all your solder joints and make sure you don't have any shorts. Also go through it with an audio probe to see where the signal is getting hung up.