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, September 18, 2018

AMZ Overdrive Pro

An oldie, but a goodie (I assume–Jack designs good stuff). It's a unique high gain design with a 3-band EQ. In Jack's own words:

It was made by combining the following circuit fragments: input gain stage is the Muffer, followed by the IC gain stage of the Fat Gnat, a tone control from the Fender Pro Roc amp and the output buffer of a TS-808! High gain boutique sound at its best, though not a clone of any existing pedal.
Here are some ideas for mods that can allow you to customize the sound for the best response with your gear:
  • Use a bipolar opamp for IC1, even the LM741 will sound good!
  • If it is too fizzy sounding, increase C5 to 270pF or 560pF
  • For more bass response, increase C4 to 2.2uF or 4.7uF
  • Use red LEDs for D1 and D2 for more output
  • The tone control shown on the schematic has a big mid-range scoop. If you would like a more traditional response, increase C8 to 470pF or even 1000pF
Several people have complained about the low output of this pedal. The easiest fix is to change the clipping diodes to LEDs as suggested above. Not only does this increase the output but it also allows better control over the range of clipping. If you want slightly more output and some added even harmonics, just replace one of the clipping diodes with an LED - doesn't matter which one.

Here's the schematic for reference. I laid it out for board mounted pots in a 125B with top mounted jacks.


  1. Verified!
    Great sounding tweakabl ditortion, but you definitely want to teek with some of the values to tame the fizzyness down a bit. I have built it with switchable clipping section: 1n4148 pair, whit 3mm LED pair and Ge pair, however the Ge is not loud enough. Here are the values I used: R2 = 220K, R4 = 1K5, C4 = 2u2, C5 = 680p, C8 = 560p, IC: LF351.
    Also, the 2n2 capacitor was not fitting to the defined place. I use box type capacitors. One can put it a little higher in the places of the diodes.
    Maybe it is a good idea to cut the copper trace on the top of the PCB, to avoid ground loop.

  2. One more thing. The 470nF capacitor covers the hole of the Bass pot. At least for me this was the case.

  3. Gain pot works reversed. The one which is now lug 3 should go to lug 2. lug 1 to lug 1.

  4. Great sonic flexibility, but I found it a tad too strident and fizzy for my amp and tastes. I tamed the high end by increasing C5 to 390pf and raising C7 to 3300pf.

    It's probably also useful to stick a 100R fixed resistor between ground and the ground end of the Saturation pot. That way, you can turn it all the way down, without turning it "off" and mistaking it for some malfunction.

    The tonestack values are fine, but depending on your own guitar, amp, and tastes, you might find some value in playing with the Duncan Tonestack calculator and trying other values.

  5. I need help, how to add middle sound? in this circuit the middle tone disappears ... and the treble makes the ear hurt .. Solution?