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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.
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14 comments:

  1. plushAugust 12, 2016 at 11:43 AM

    Thanks, gonna try it tomorrow

    ReplyDelete
  2. plushAugust 13, 2016 at 11:58 AM

    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

    ReplyDelete
    Replies
    1. plushAugust 13, 2016 at 12:52 PM

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

      Delete
    2. UnknownAugust 15, 2016 at 4:30 PM

      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.

      Delete
    3. plushAugust 16, 2016 at 5:12 AM

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

      Delete
  3. plushAugust 16, 2016 at 2:28 PM

    Thanks Cody, it was my fault

    it works and sounds great, but it is freaking loud

    ReplyDelete
    Replies
    1. UnknownAugust 16, 2016 at 2:45 PM

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

      Delete
    2. plushAugust 16, 2016 at 5:38 PM

      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.

      :(

      Delete
    3. LUBDARAugust 21, 2016 at 4:53 PM

      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!!!

      Delete
  4. LUBDARAugust 21, 2016 at 4:51 PM

    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 😀

    ReplyDelete
    Replies
    1. UnknownAugust 22, 2016 at 4:01 PM

      I always look forward to what your cooking up!

      Delete
  5. IvMAugust 27, 2017 at 7:29 PM

    Would a ~100hfe (as the hfe listed on mps05's datasheet) NPN transistor work fine there?

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    Replies
    1. Effects LayoutsAugust 27, 2017 at 8:33 PM

      100hfe is the minimum with the MPSA05. I would think others would work as well, but that might require some tweaking.

      Delete
    2. IvMAugust 27, 2017 at 9:45 PM

      Sure David, thanks.
      I'll see with some 2n2222 that are almost there.

      Delete