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Wednesday, 14 March 2012

Mictester - Silicon Tonebender

If you're into fuzz then here's a gem for you - a super consistent silicon fuzz monster. Here's the schematic and vero layout. For more info here's the freestompboxes.org forum topic (*complete with attached bitching over circuit credits and origin*): http://www.freestompboxes.org/viewtopic.php?f=13&t=7767

Here's mictester's advice on tweaking:

"Adjustment: set the 1k "Abuse" pot halfway. Play though it, and adjust 5k preset until "gating" just stops. That's it!

You'll find that it has plenty of output, that the "Abuse" control gives a good range of colour, the "Sparkle" control has a very wide range and the sound is remarkably reminiscent of early Jeff Beck (certainly not a bad thing!).

Possible mods:

Put small value capacitors from base to collector of the middle two transistors - start with 47pF. This "smooths out" the sound a lot, but reduces the treble available.

If you have radio interference, put 100pF from base of the first transistor to ground.

Experiment with the capacitor values in the tone control - the 8n2 could go as low as 3n3, which would give a ridiculous range of treble control!

Increase the value of the 47k feedback / bias resistor - try as high as 470k. The gain will rise, the touch sensitivity will disappear, and it will become a high gain screaming monster! "

Now - here's a similar design posted back in 2003 by Gus Smalley; the "Hot Silicon":

Take away the furore over circuit credits and what not and you've got a great sounding design here - it's an absolutely cracking fuzz circuit (I actually prefer it to messing about with Germanium transistors!). Give it a try - you won't be disapointed!
And here's an image of a completed build by LaceSensor:


  1. Hello, has anyone tried the vero board layout here? I have had trouble getting it to work. Any advice welcome.
    I have tried exchanging the 10k resistors on the collectors of the BC109Cs but to no avail. I did get a buzzy signal through at one point but not now. I also tried 10k trimmers in series with the 10k resistors on the collectors, but again no joy. One thing I did wonder is should there be a link between pin 1 and 2 on the VR to ground? Regardless of this I should get a signal I reckon. Anyway, might just draw my own vero layout like normal. That's what I get for taking shortcuts :P.
    Anyway, if anyone can verify the board layout is correct and works, this would be great.
    cheers - Brett

  2. This comment has been removed by the author.

  3. Probably a little late, but for anyone else who come across this, yes the board is correctand works. No, the trimmer does not need lugs connecting: The uppermost lug is not connected to anything, the other two lugs form a variable resistor that adjusts the bias of the third transistor by altering the emmitter resistance to ground: It allows you to dial in anything from smooth and sustaining to gated and splatty.

  4. Простенько и со вкусом. Винтажный звук со всеми косяками винтажа.

  5. It's a strange story....

    A friend bought a silicon bender from Macari's in the late 70's. He put it away in a box of junk for a few years because it sounded terrible!

    One day - a few years later - he and I were looking for a box to build a fuzz into. He remembered the "terrible" Macari's Colorsound effort in his junk box. We cleaned out the battery gunk that was inside the box (!), fitted a new battery and cleaned the pots. We tried it into my little practice amp, and all it gave was nasty "fart" sounds and no sustain. A few minutes with a multimeter showed the problems. The transistor bias was all over the place, with the final transistor collector "bottomed" because the base to ground resistor was dry-jointed!

    There followed an evening of experimentation and resistor tweaking. After a couple of hours, we got the values that are in the FSB posting. It's probably the best silicon fuzz that you can make.

    I've built them with super low-noise transistors (ZTX384W - complete unobtaineum), I've built them with old-fashioned transistors (BC109C). I've built them with low gain transistors (2SC828), and ultra high gain transistors (2N5088). I've even built them with transistor arrays (CA3089 - Lance's "Fuzz Chip"!). Each version has it's own character, but none of them sounded bad.

    My favourite - and the one I make quite frequently today - uses BC550C all the way through.

    I have redesigned my PCB a couple of times over the years, and the latest version has two complete fuzz circuits with trimmers rather than external pots, relay switching, and two momentary foot switches to select each fuzz. If "A" is selected and you tread on "B" it changes over. If "A" is selected and you tread on "A", the effect is bypassed. If "B" is selected and you tread on "A", it changes over. You can't ever engage both fuzzes at the same time!

    It's an easy build, and sounds great every time!

    1. Here you are posting this same nonsense story all over the internet. You obviously stole this Gus Smalley.

  6. By the way - I didn't see Gus Smalley's effort until well into this century. A lot of people have been playing my earlier silicon fuzzes with DPDT foot switches since the early '80s.

    Have lots of fun with this circuit


    1. Yes, it's sounds very well, I love it.
      I have a problem anyway: I can't adjust the trimmer... gating doesn't stop completely. I've tried many transistors and I've changed some trimmers but I cant' solve my issue. Any idea?


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