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, January 27, 2015

ESR Graphic Fuzz

Gnarly, oscillating fuzz tone–this is a bit of a weird one. The original used both positive and negative 9v (which I have a hard time wrapping my head around). FSB forum member Induction altered the circuit to support standard power supplies, so no need for a 9v battery or adding a +/- converter. And it should sound very close to the original. Here's his schematic for reference. Should easily fit in a 1590a

Here's a demo of it against an IdiotBox Blasteroid:




8 comments:

  1. I built this tonight and seemed to run in to an issue. Here are my voltages first

    LM741CN
    1 0v
    2 2.1v
    3 1.7v
    4 0v
    5 0v
    6 2.1v
    7 9.5v
    8 0

    I am getting clean signal on pin 2 and I am getting distorted signal on pin 6 but the volume seems to be only outputting clean signal. I have checked my pot pin out 3 times now and everything looks good. Suggestions?

    Cody

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  2. I noticed last night that the 2 10k resistors at the bottom of the layout need to be connected to pin 3. Just updated the layout so now it should be correct to the schematic posted above. Not sure if that would contribute to you just getting clean output, but give it a try. I'm not great at troubleshooting, but you might want to socket the 1µf output cap and see if that could be cleaning up the signal between it and pin 6 (tho I kinda doubt that's the culprit).

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  3. Thanks for the update. I etched and built it tonight and it worked and sounded like the demo. I did notice that this thing howls when the volume is down the then the filter will adjust the tone of the howl. If I get the volume up past 20% the howling will stop unless you turn the filter all the way up like in the video. I know Tabbycat is still tweaking this layout a bit in FSB so I will watch that thread also. This thing really does sound great though. Can't wait to get to crank it up.

    Cody

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  4. PCB layout verified as well. At first I got nothing but squealing/oscillation. I went back to the bench twice to check everything out. Then I hooked it up again and noticed the bass roll-off knob was set on my guitar. I backed it all the way off and it sounds much closer to the vide.

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  5. Built it. Squealing is too loud most of the time, how could I keep it down?I used polyester caps rated 400v, and it sounds pretty close to the original on the video. Thanks for posting this!

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    Replies
    1. This thing is really sensitive to input impedance, so you may want to add a buffer to it (the AMZ simple JFET buffer would work well). EBRAddict over on FSB recommends having the buffer feed pin 2 of the IC.

      http://freestompboxes.org/viewtopic.php?p=250813#p250813

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    2. I built the amz simple jfet buffer and it makes it stable, but I had to change the filter pot to 10k to make it usable, because 99% of the rotation was almost useless. I don't know if it's my build or what, but now it sounds amazing, really. Thanks!

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