Rab/Kay Fuzztone Finished Pedal

Posted: 2010/07/19 in "Rab Fuzz"/ Kay Fuzztone Clone, DIY Guitar Effect Pedal Projects

After installation of the conversion circuit board, it’s a Kay Fuzztone clone.   I’ve nicknamed it the “Trab Fuzz.”  🙂  Here’s what the finished pedal looks like – basically a stock Crybaby wah except for the blue LED and extra knob on the side.

It’s under the hood where things are clearly different from a stock wah:

  1. Brian Kinnaman says:

    Looks great! Are you going to sell these?
    I made one very similar to that would love to hear yours.

  2. Will says:

    Hi, I was wondering if you would post the entire schematic up sometime including LED’s and connections to pots etc? The one on the page is incomplete according to you and I want to try and build this thing! 😉

    wow though, looks amazing! If you don’t want to post your whole schematic, could you point me towards another complete one?


    • trabantland says:

      Thanks. Actually the schematic does show the connections on the pot. If you want to build one yourself (and I assume you haven’t done this before) you should look at this wiring diagram: http://www.generalguitargadgets.com/diagrams/switch_lo_3pdt_ig_dcjack.gif. Once you understand that wiring you’ll be able to add true bypass wiring to any effect, using a 3PDT. This diagram will show you how to hook up a footswitch to the circuit and also the LED. Also, if you want a layout you can use this one here: uStomp Kay Fuzztone.


      • Will says:

        Thanks so much for putting in the time to reply, I really appreciate it! I’vbe bought a broken crybaby for cheap and I’m really looking foreward to building myself a kay fuzz!

        Thanks again and the SDD-3000’s also sound amazing btw!

  3. Will says:

    Hey again! I hope you don’t mind me asking a couple of questions about the build? If you don’t want to answer, feel free to tell me to go away!

    What is the speaker like looking thing on the left side of the build diagram on this site? http://ustomp.com/?p=5 Is it a battery? And if so, how would i remove it from the circuit? Ie. how would i build the pedal but without the facility for battery power?

    Also, the wah enclosure I bought doesn’t have a hole for the wah and Im not sure Ive got a drill powerfull enough to go through cast metal! What circuit alterations need to be done to not include an LED? Ie. If I simply remove the LED, R LED and the wires connecting it, will this have any bad effects on the rest of the circuit?

    Thanks again, and if you ever need anyone to trial your future pedals I’m available! 😉 I’m a much better player than I am tech!


    • trabantland says:

      You’re right- that symbol on the left is a 9V battery clip. If you want you can leave it off with no harm done. If you look at the DC power jack you’ll see the battery is connected to the switching connection. This is so the battery isn’t in the circuit when you connect an adapter. Just ignore it and the connection to the DC jack – You’ll be fine.

      Yes, you can also ignore the LED stuff if you want. Also you’ll save some money since you don’t need a 3PDT switch that way – a DPDT will be fine. The center part of the 3PDT switch just connects the LED to ground to turn it on.

      • Will says:

        Hi again Dave, just wanted to say I have pretty much finished my clone and cheers again for the help you provided! I shelved the project for ages then last week built a prototype on a bread board and I have now pretty much finished the proper version and I have learned an immense amount about electronics on the way!

        I was wondering how you get your clones done on PCB’s? Do you have a company do that for you? Also the main problem with making clones seems to be what to build them in! I have a mate who would quite like a clone too, did you just get crybaby chassis off the internet or something? There doesn’t seem to be much alternative!

        Anyway, thanks!

      • trabantland says:

        Hi Will, Yes, I designed the PCB myself and then have a company print them for me.

        I generally find that used Crybaby housings are the best option for this. They’re rugged, and you also get a 100k pot included.

        Small Bear Electronics sells a new wah/expression casing that also works:


        But you’ll still need to buy the other parts – switch, potentiometer, and jacks, etc.

  4. Frank says:

    Hi, my question is about the second pot,
    that you placed outside on the wah unit.
    In the schematic is no signs there.
    What funktion does the pot do??
    And where to put in??
    With best wishes

    • trabantland says:

      Hi Frank, that pot is a simple little mod I came up with for the circuit. Basically you can replace the 10k resistor, R10, with a pot instead of a fixed value, and this allows you to adjust the bias on Q5 and Q6, giving you some extra tone-shaping options.

  5. Hi! Do you have any diagrams of the PCB on this thing? and would there be any way to wire it up to a second switch that could switch between a regular crybaby circuit and a fuzztone circuit? I have an old 70′s crybaby, but i love it’s sound, and I don’t want to buy another wah just for this. Is there any way to do that so it’s basically 2 effects in one?

    • trabantland says:

      Well almost anything’s possible but it would be tricky to do. And either you would need a dual-ganged potentiometer (which probably wouldn’t fit, I’m guessing), or an additional switch to move the connections on the pot from circuit-to-circuit, assuming you want to use the same pot on both circuits. So to do this would require a totally new circuit board that incorporates switching between two different effects for both the 1)input, 2) output and 3)potentiometer. With so many connections changing simulatnaneusly, I would probably do it using relays.

      • Could I have the wah circuitboard in there along with the fuzztone board, and just have the pot wired to both, and then have a switch right before the output?

      • trabantland says:

        The problem with doing that is that the circuitry from one effect can interact through the pot connections with the circuitry from the other effect. I think you’ll need to totally separate them.

      • Well if that’s the case… are you still selling these?

      • trabantland says:

        I have sold out of all them at the moment. If there’s interest I may make some more.

  6. Petetheroadie says:

    I’d love to get my hands on one of these if you’re up for making another batch!

    • trabantland says:

      Thanks Pete- I may make some more in the future if there is some more interest. If I can find at least 10 people interested in one I will make up another batch of circuit boards.

  7. pierpaolo says:

    Hi Dave, my question is about the relay,i don’t find it in the schematic.What function it has?

    • trabantland says:

      The relay is simply part of the switching circuit – but you can use any switching circuitry you like. The schematic shows the audio circuit (which is what counts). If you do a quick search you can find instructions for true bypass wiring in many places.

  8. pierpaolo says:

    thanks you, i’ve found all the instructions for true bypass.just another question:in this build diagram http://ustomp.com/files/kayfuzzbuild.pdf there is a resistance on the left, (1M = 1Megaohm ? it’s possible?) between the 22k resistance and 10uF capacitor,wired with the GND.it isn’t in the schematic,is it necessary? thank you very much for your help.

    • trabantland says:

      That appears to be a “pulldown” resistor, added to reduce popping noises when switching the unit on and off. It’s optional, so you don’t absolutely need it. You can try without and then add it later.1M and 2M are common values for those.

  9. Victor says:

    Hi Dave. Looking at your board there is two extra caps, a big electrolytic and a ceramic cap. What is the function of them? I’ve made the ustomp kayfuzz but it doesn’t sounds like yours. Do you have any sugestion? Cheers

    • trabantland says:

      Those are just extra power filtering and not part of the audi circuit- they won’t have a big effect on the sound. What did you use for diodes and transistors? Dave

  10. trabantland says:

    Hmmm strange. Those are all good transistor choices. Are you using the BC550C? If so I think you could go for a lower hFE there but it should still work fine. I agree that Germanium is the way to go on the diodes.

  11. Jason says:

    Hi Dave,
    Built a clone a while ago and although it works it’s not dependable enough… do you still have a stock of your fuzztone pcb’s?
    And if so can I buy one!

    • trabantland says:

      Jason, I’m sold out of the Kay/Rab Fuzz boards but I’m working on a new design so those may be available in the future.

  12. hi dave,
    i built the circuit on vero, but ran into some issues. i used to have one of the original units back in the early mid 70’s, and the only way i can get it to sound right is with the ge diodes…but the volume drop when engaged is pretty extreme. so i went with a combo of silicon and ge in the clipper, which got me close enough to unity gain for rocknroll, but the tone is funky…and the whole bloody pedal works more like the old kay wahs than a fuzz now.
    weird planet.
    i know it’s asking a lot, but any chance you could measure and post the voltages on q1 and q2?
    to be fair, i did stray slightly from the posted schem…
    my build uses 2k rather than 1.8k resistors, and for transistors i socketed and tried the original 5088’s for q 1&2, and a matched pair 0f 3904’s for q3&4..didn’t sound like i remembered at all.
    ended up with mpsa18’s in q 1 and q3, which seemed to help. also added a 1m pulldown resistor from input to ground, a 220r “smoothing” resistor to the b+ supply, and a 4.7k resistor for the led.
    mismatching q3 and 4 made a huge difference in the overall tone, especially 2nd harmonic content.
    it sounds like the original (well, a little better) if i run a fuzzface into it, but on it’s own, very little distortion which is weird, cuzz i remember mine almost sounding like a superfuzz!!
    any help would be appreciated, i’ll gladly post the vero if you want once the bugs are worked out.
    the voltages i’m getting on the transistors are as follows (it does make a nice wah sound this way, tho)

    e 6.10
    b .82
    c 5.45

    e 5.46
    b 6.10
    c 5.45

    e .26
    b .81
    c 7,80

    i’m stumped…appreciate any help!

  13. fwiw, here’s the vero i knocked up:

    i’ve gone over it again and again, and can’t figure out where i went wrong!! 😉

  14. hi dave,
    i’m an idiot, as usual. 😉
    got it. had to add a 100k trimmer (set to about 63k…68 didn’t work well enough, i tried just tacking a resistor on) in parallel

    with R10 (on the vero). could then tune the fuzz in til it sounded right.

    seriously have no idea what i did…or at least the math involved, but it worked…i guess divide 100,000 into 63.000 or something? i’m a hack.

    final voltages were a lot better after this:

    e .25
    b .83
    c 5.45

    e 5.23
    b 5.84
    c 5.84

    e 1.40
    b 1.93
    c 2.03

    e 1.40
    b .87
    c 1.40

    i don’t know if these actually look better, but it sure sounds more like i remember it.

    add an lfo to sweep the tone pot, and i bet you have the lost psychedelic machine. it doesn’t sound like a wah as much as a phaser.

    it’s amazingly similar to some of jimi’s mild fuzzed out univibe sounds (“gold and rose, the color of the dream i had”)

    i gotta gig tonite, will post a clip soon.

    if dino or ian are paying attention, it’s VERY mouthy, kinda like the mr multi a little…but fuzzier in a good way. a hint of formant.

    anyways…thanks for looking. if i ever get around to it, i’ll update the vero with a 100k trimmer.

    if you attempt this, beware…the sweet spot between too clean “wah” and too fuzzy “fizz” is an extremely narrow window, between about 59k and 65. below or above either harsh distortion or way too clean.


  15. hi dave,
    just a side note, now that’s all said and done.
    revisited it yesterday again…as it seemed to change in tone overnite a little…gotta love germanium!
    the original did, too.

    anyways, i’m calling it done. final mods were a 10pf between e & b of q1 to nuke the ultra highend..not necessary if looking for the original sound, but less power line hash that way.
    also replaced that one resistor with 100k trimmer…i’m imagining i could ditch the silicon diodes and use that to get it to unity gain, but too lazy atm.

    thanks for a very fun and satisfying project. i housed mine in a plastic “rogue” wah shell for authenticity and bizzarre radio interference.

    this thing sounds GREAT after a fuzzface…almost like a synthesizer, just a shade of formant too.

    fwiw, i believe a 50k pot may work better than the 100k…too even out the sweep a little. i have mine set from pot fully down at heel to wherever the rotation stops.

    gonna try and do a demo, will post a link back.

    again, thanks mate…


    now…on to the kay tremolo

    • trabantland says:

      No worries…Glad you’re having fun. 🙂 100k works fine for the pot but one thing you can do (instead of searching for a 50k pot) is replace the 100k resistor that connects from pin 1 of the pot to ground with a trim pot. This allows you to adjust the volume in the “toe down” position, so that it’s more even with the volume in the “heel down” position. I definitely prefer Germanium over Silicon myself but some people do like the volume boost. Dave

  16. my build with germanium sounded right, dead on, in fact! but there was too much of a volume drop with true bypassing the effect. the original just switched the tip of the jacks if memory serves…that’s the only reason i used silicon too, was to try and find a mid point where i had enough volume, but didn’t lose the tone. straight silicon leaves you a wah wah pedal!

    the ge is the heart and soul of it..i may just bite the bullet and go back to ge and put a small booster inside to get it up to unity.

    this was another of the pedals of my youth i’ve been lusting after…thanks to you, i’ve built it!

  17. hey dave, here’s a quick video of mine,
    the dang treadle mechanism broke, but you can hear the fuzz on it.
    i took it apart to fix it after the video, and replaced the clippers with more germanium, big improvement.

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