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, August 12, 2016

Evil Harmonic Overdriver

For Fuzz Friday here's a really cool circuit designed by Lubdar over on the Madbean forum. It's inspired by Death by Audio designs and can go from overdrive to full on fuzz. If you can't get a DBA design working, give this one a shot. Here's what he had to say about it:

It's a combination of ideas from the newer Evil Fuzz/Harmonic Transformer/Interstellar Overdriver.
It is comprised of 2 reverse beta gain stages, with level controls for each, that way you can turn level1 all the way down and get fairly clean overdrive tones, or max it out for fuzz, and anywhere in between.  The density knob controls the input capacitance for thin treble all the way to bass bass bass.  The toggles are for switching out a transistor stage in the 1st gain stage, and the second is an output pulldown resistor to give a slight volume boost.



11 comments:

  1. I've build one using mpsa06 with hfe around 230 and i don't think it works as was intended.
    Density knob is very loud
    Pre and pos pot values are way too high
    Shape switch just cuts signal to 0
    Boost adds masses of gain, blasting my ear drums

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    1. Sorry, density knob does virtually nothing.
      Post is loud af
      Pre is meh

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    2. With the shape switch, did you make sure you followed the pinout since they are not in consecutive order. Its easy to over look. On the layout its listed 1,3,2 and the switch is number 1,2,3. Just want to verify.

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    3. Oh god, this could be the issue. Thanks, Cody, i'll check it today.

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  2. Thanks Cody, it was my fault

    it works and sounds great, but it is freaking loud

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    1. Awesome! I think "it is freaking loud" is DBA's mantra. lol

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    2. it's VERY loud, i mean, it's enough to turn the "post" pot for like 1% to get decent output, but everything past it is so loud that it becomes almost impossible to use it in pedalboard

      I'm afraid that i can accidentally touch "post" pot with my foot and it'll destroy my amp, my cabinet and my whole neighborhood. I'm not joking.

      :(

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    3. If you leave the clip switch two down, that should be shunting some of the signal to ground and keep the volume from overpowering things...or at least that was what it was intended to do. Everything fully open is crazy loud!!!

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  3. Thanks for the feedback you guys, first design could probably use some tweaking... maybe different pot tapers, different cap values may have more of a dramatic effect throughout the density pot sweep. The pre-post was to mainly try and get a somewhat clean boost. I'm about to move and will have to potentially pack up the breadboard for a while, but I appreciate all the feedback thus far 😀

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    Replies
    1. I always look forward to what your cooking up!

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