Tuesday, 1 January 2013

Amtron UK854 Fuzz Box

This thing is close to a classic Fuzz Face, but just by looking at the schematic, i seemed like this baby has tons more bass and wilder fuzz control with much higher values than its idol. Simple and small, but some of you Fuzz Afficionadas might find this good thing to build.

I promise not to post any more Fuzz Face derivatives for a while :)

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Edit! Just built this, and as i suspected, the stock value of 27K is not biasing my 2N2222s correctly. Replaced that with 5K1, and now i have bassy vintage fuzz tone :) You might need to find a value to match your transistor instead of that stock value.



Here's rejigged layout with stock 22K resistor replaced by 25K trimpot. That should let you bias your favourite transistors correctly.



17 comments:

  1. Thanks, Looks interesting.
    You guys have been busy :)
    Would it be a good idea then to replace the 27K with a trimpot?

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    1. Yes. That would be a very good idea. I don't think i'll be drawing these anymore - as the designs are flaky and the bias gets nailed only with some obscure/obsolete transistors with default values.

      Seg@fredo: What do you think - should i update the layout to accomodate the trimmer? That could lower the frustration of building this with different transistors but with stock resistors...
      +m

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    2. Perhaps (if you feel like it) you can add it as a modded version. But please no rush :)
      I don't know if i'm going to be building this in the near future, but i have been looking for a good fuzz-face-kind of pedal and since i play bass most of the time this one caught my eye.

      Thanks for the quick response :)

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    3. Yup. I think i'll rejig this and Schaller fuzz for trimmers tonight.

      Have you tried just a basic Fuzz Face with bigger in/out caps for bass? I think that should do it.
      +m

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    4. I have been looking at the Joe Bonamassa Fuzz Face but it seems that the specific transistors are very hard to find.
      I recently did the zvex fuzz factory veel layout. Sounds awesome on guitar but not realy suitable for bass.
      By the way... My next project is going to be the Rock Box Boiling point, for guitar that is :)

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    5. Thanks for the advice on the caps though.

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  2. Thanks for the mod layout.
    I'll add the missing parts to my shopping cart so i can put it together anytime soon.

    By the way... did you bias to a specific voltage or mainly by hearing?

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    1. By ear. JFET circuits need to be at exact voltage, but BJT bias isn't that crucial when it comes to voltage. When it's correct - you'll hear it.
      +m

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  3. Finally put this one together but i get very low volume, much lower than my clean signal. And almost no sustain... like the signal is gated.
    I'll try to sort things out on breadboard first.
    I used two 2N2222's.

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  4. With some help i found the problem...
    Fuzz pot should be a 470R an not a 470K
    I used a 500R pot and it works great.
    Still used 2N2222A but i'm gonna try some other npn's as well

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    Replies
    1. Super weird.. But you're correct. I'll fix the label.
      +m

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    2. I mean - i clearly remember this working once i built it... Don't know where the board is now though.
      +m

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  5. This one made me dive a little deeper in to the theory of the Fuzz Face circuit and knowing some background theory is never a bad thing ;)
    And you where right... the schematic is somewhat different than a classic fuzz face but it does have that 'vintage' tone.

    Thanks for the post!

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  6. Is it possible to use a 10k trimmer instead of the 25k?

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  7. I finished the build and got great results with a 10k trimpot and omitting the 470r pot in favor of a 470 resistor at lugs 1 and 3 while also switching the 100uf anode from Fuzz 2 to Fuzz 3. I'm going to pick up the 470r pot and a 25k trimmer just to see the difference. Great bassy fuzz tone.

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  8. Please...: url schematic!

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