“Rab Fuzz” Project

Posted: 2010/03/27 in "Rab Fuzz"/ Kay Fuzztone Clone, DIY Guitar Effect Pedal Projects

Here’s something a little different from the other projects documented so far – a project designed for you to complete.  This thread will be devoted to building a “Rab Fuzz” or Kay Fuzztone clone from an old wah pedal enclosure.   The Rab Fuzz is used by  The Edge for the song “Elevation.”  You hear it mostly during the intro riff to that song.  It’s so named (designated as RABFUZ on Edge’s pedalboard) because as the story goes, one of U2’s technicians, “electronic wizard” Colm ‘Rab’ McCallister, took an old Kay Fuzztone pedal and rehoused the circuit in a sturdier enclosure for The Edge.  (Original Kay Fuzztones are made of rather flimsy orange plastic.)  The Kay Fuzztone was introduced to The Edge by Daniel Lanois during the recording sessions of All That You Can’t Leave Behind.  “Elevation” was the song U2 wrote around a riff played by The Edge using the effect.

This circuit replaces some hard-to-find components (transistors and diodes) with easier-to-find modern replacements, but the “Elevation” sound is all in there…

First, here’s a partial schematic of the circuit board (not yet showing complete wiring of the jacks and switch, etc.):

 

 

Changes to the original circuit include using 2N5088 transistors for Q1 and Q2 instead of 2SC644S, using 2N3904 transistors for Q3 and Q4 instead of 2SC828R, using 1N914 diodes for D1 and D2 instead of OA90, and changing the value of the potentiometer to 100k instead of 50k.

Edit:  I would like to add as and aside, that after testing several different diodes in this circuit, I personally think Germanium diodes are the way to go rather than the (Silicon) 1N914.  The 1N914s sounds good, but you get a bit of a volume boost since they clip at a higher threshold than the Ge diodes.  (This may or may not be to your liking.)

 

 

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Comments
  1. Jason says:

    Hi there,
    I’ve had a dud wah laying around for a while and this looks to be within my skills. I’m relativly new to pedal building so wondered if you had a veroboard layout and components list that I could follow for this pedal….
    Cheers,
    J.

    • trabantland says:

      Hi J. – I don’t have a veroboard layout, but there is a DIY etch pattern at ustomp.com…I am planning to make a my own circuit board for this and I will be posting the component list.

      Cheers,
      Dave

  2. jason says:

    Dave, great to hear you’re attempting it as well…. Would you mind sharing your parts list as I’ve seen a few posts relating to the pedal on “Freestomp…” with some unable to source the exact items…. Are you a member?… I was chating to “Roseblood” the other day and he also had the ustomp board but hadn’t populated it yet… Just been looking at youtube demo’s of how to DIY etch a board….. Not sure if I want to mess with all those chemicals…. think I’ll keep looking for a vero version.
    Will keep you posted how things happen when they do…
    Regards,
    J.

    • trabantland says:

      Hi Jason, Yes I will post the parts list next in this thread – if you look at the schematic you’ll see that I replaced some of the hard-to-find components with more common ones that are easy to find.

      Here’s an idea – If you don’t want to etch the board yourself, you could email the ustomp board .pdf to JD Sleep at General Guitar Gadgets (http://www.generalguitargadgets.com/) and ask for a board. I don’t know if he still does this, but I had him custom etch me a board once in the past and it wasn’t very expensive at all ($10-$15).

      Cheers, Dave

  3. Jason says:

    Hi Dave,
    Been busy lately but wondered how you were doing with your Fuzztone… Wondered if you could cast your eye over this vero for me. Would this work? (taken from the Kay Fuzztone thread @freestomp…) I’m hoping to do an order soon as the diary is a little clearer now….
    Speaking of being busy how is the SDD3000 2.0 coming along. I saw the new prototype pic… what’s the waiting list like? I’m very tempted as it sounds very, very good.

    Regards,
    J.

    • trabantland says:

      HI Jason, The fuzztone is coming along, I’ve been experimenting with the circuit so far. I only gave your veroboard layout a quick glance but it looks pretty good. It’s using the original transistors and diodes, which may be hard to find.

      Cheers,
      Dave

  4. Jason says:

    Dave, thanks for getting back…
    Sounds like you’re about to unleash a “souped up” version of your own…
    Do you see improvements over the original?
    As I’m in the UK, you’re correct about the vintage parts availability!
    There are a couple of sites… not many though and I haven’t got as far as prices yet… so….
    From your knowledge would I be able to use my vero layout but substitue the tranies and diodes that you quote in your parts list? I’d expect the pin outs to be different but would I need to change anything else….
    I’m foaming at the mouth to build this!!
    Regards,
    J.

    • trabantland says:

      Yes, J. you’ll be fine with these transistors, just watch the pinout (E-C-B etc.) and make sure they go where they need to.

      For diodes I’ve tried a bunch of different ones – with Silicon diodes (1N914 etc.) you get a nice volume boost (compared to Germanium) since they clip at a higher volume.

  5. Jason says:

    Hi Dave,
    It’s been a while but I see you’ve been busy with the amp build and the SDD3000 pedals. How far did you get with the manufacture and sale of your Kay Fuzz clone PCB’s? Have had mixed results with my build so I’m considering all options! I used OA91’s but had trouble with the sweep of the tone pot… not giving the pronounced pulsing effect ala Elevation….mine is heading for the breadboard, I really can’t let this one go! Ps is this your pedal in action?http://www.youtube.com/watch?v=kUgH0VEMtHI

    Cheers,
    J.

    • trabantland says:

      Hi Jason, Actually I have some plain boards for sale if you interested. The pedal in that clip is by a guy on U2sound named Zach, a nice guy too. I actually had one of his pedals but I think my mods sound a little better (personal opinion). He used silicon diodes, but you get volume boost that way which I don’t like. Your other option is to order a PCB based on the ustomp.com pattern, which is fine. These are all good options – I think my board just makes the wiring faster/easier.

      Dave

  6. jason says:

    Hi Dave, thanks for getting back,
    Yes I have to admit that the PCB option is attractive as I’ve built 4 vero’s so far. The last two actually worked but not faultlessly and still with a fair bit of crackle at times…

    So begs the question, how much silver to cross your palm!

    Cheers,
    Jason

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