Sunday, 5 August 2012

MI Audio GI Fuzz

6 knobs plus a Bright switch, and still needs an onboard trimmer.  I will be extremely impressed with anyone getting this in a 1590B!  Basically it's a modded silicon Tonebender MkII and it must be one of the most tweakable ones out there so I'm sure it would be a great addition to many peoples collections.

Info from MI Audio about their original:

The GI Fuzz is a high gain fuzz design, featuring a trio of ultra low noise, high gain silicon transistors. This is not a fuzz for the faint hearted. It has about 20db more gain than a Fuzz Face, so you can think of the gain achievable as being equivalent to a a Fuzz Face at full tilt being driven by a booster! This is military spec fuzz, complete with a camouflage green aluminium enclosure and stencil script. The GI Fuzz is not a clone of anything out there.

MI Audio settled on a design which makes the GI Fuzz one of the most versatile fuzz pedals out there. At last, the fuzz pedal has joined the 21st century! No longer the 2 knob, unstable, radio receiver of yesteryear. You get 6 knobs, an internal trimmer, a 3 position switch, and the ability to create anything from fat bluesy tones, to traditional fuzz, to all-out sustain, to gated, synth-like bleeps.

  High Gain silicon fuzz.

  Fuzz generated by a trio of high gain silicon transistors

  Ultimate flexibility with the following 8 controls (1 internal):

        ● Fuzz - from nothing to all out fuzz
        ● Load - input impedance control
        ● Bias - controls the bias of the 2 transistors
        ● Body - midrange control
        ● Tone - balancing control for controlling highs and lows
        ● Volume
        ● Bright switch
        ● Internal Gain trimmer.

  Professionally powder-coated and silk-screened enclosure, measuring only 4.3" x 2.2"

IN DEPTH CONTROL DETAILS FROM MI AUDIO:

  A huge gain range, from nothing to sustain-for-days

  It can be used as a low gain device (for a fat bluesy bite), which is fairly unique for a fuzz pedal, since fuzz pedals tend to have a very narrow range of gain.

  To tame this pedal, there's an internal gain trimmer to wind things back (which I recommend)

  Load control, which is a variable input impedance. This can be used to match the GI Fuzz to humbuckers as well as single coils (Fuzz pedals tend to have low input impedance which is a better match for single coils. Now you can also use humbuckers without any problems). You can also use it to go from a tradition fuzz sound (low input impedance) to a more articulate sound with detailed highs (high impedance)

  A bias control to set up the operating point of the transistors, from a fat symmetrical fuzz, to an asymmetrical 'mosquito' buzz, and beyond, to a gated synth-like sound (almost sounds like your amp is about to die!)

  Body control, which full range mid range control. The mids, of course, are the most important frequencies for determining how your guitar tone sits in with the rest of the band.

  Tone control, which controls both lows and highs, as opposed to simply a high cut filter. This is like bass and treble controls rolled into one. The combination of the tone and the body controls is like having a low/mid/high EQ

  Volume control with output to spare. You can use the GI fuzz to overdrive your amp.

  3 position bright switch to help tame the top end. This is useful if you're going to use your GI Fuzz with a bright 'modern' voiced clean channel, or if you're going to use the GI with overdrive pedals (which tend to be darker, and by comparison, make a normal fuzz sound shrill).






37 comments:

  1. Just out of interest, Is it possible to buy those mini pots anywhere?

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    1. Rapid have some 9mm pots Vince, but I don't think the range of values is extensive, probably best to try banzai or musikding I reckon dude!

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    2. Musikding has good selection on 9mm alphas. They are quite expensive though. I just wish tayda would stock them. I've been asking..
      +m

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    3. Oh right, cheers fellas. I doubt I'll buy any, I was just wondering if they were available. I'm confident on getting six regular pots in there but the switch might be an awkward son though...I've overdosed on fuzzes at the moment though so this will be fairly low on the list..

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  2. Nah. I get only noise that fades or loudens with tone and body controls. Thought i'd check this against the schem, but don't seem to find one. I may be too tired...
    +m

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    1. Ditto, although I am getting signal, it's just not great by any means. Tried it with 5088's (with reversed pin out) as I only ordered my 49C's today.

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    2. I have some BC459Cs, and they are pretty much the same as 5088/5089s according to datasheet..

      I'll go through the board and probe some.
      +m

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    3. Yup. There is a faint oscillated signal, but i wouldn't call it "working" by any means. Finally found a schem from photobucket, and took a quick look. Only difference seems to be 1u caps, which are electrolytics in the schem. Don't know much, but those could be the reason for some of the voltage getting to wrong places. I'll get my morning coffee and swap them. We'll see where it gets us :)
      +m

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    4. Darn it. No. I guess i'll need to probe it more...

      http://s698.photobucket.com/albums/vv347/harvandheavy/?action=view&current=MIAudioGIFuzztuemmuehSCHEM.gif

      I followed this schem, and i did find a fault in the layout. After C8, the 1u cap from Q3 collector to the tone section, the layout connects it only through 22n cap to tone 3. The schem i found suggests that it should also connect to other lead of 22K going to tone 1. I placed a link between the rows 4 and 5, last holes to the right. But still no.

      I'll keep on debuggin'
      +m

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    5. A little interval data.. There's something really wrong around Q2. I'll dig into it and let you know.
      +m

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    6. Cracked it. Although i think it needs to be rebuild to get the most out of it. Heh. Mark! You have some rejigging to do! :D

      The current layout "may" need these changes:
      1. C4 has it's other lead wrong. According to schem above, it's "neg" lead is rightfully connected to fuzz 2, but it's "pos" lead needs to be one row up from the neg lead - not connecting to Q3 emitter.
      2. 1µ caps may need to be electrolytic. input cap neg to south, others north, except for C4 - explained above.
      3. Tone control may need a link between rows 4 and 5. Either on the far right side (between volume 1 and body 3), or just below power filter 100µF cap.
      4. Body, Bias and Load pots may be in reverse. I'm not 100% sure about Body, since i don't have original to match it with :) Bias and Load, those i'm sure.

      Milkit! Try those!
      +m

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    7. Sorry was at a christening yesterday and have just got up with a hangover. :o)

      Yes looking at it I missed a link out and God knows what I was doing with C4! :o) Just add the link above Q3, remove the 1u to the emitter of Q3 completely and add one between rows 2 and 3 as shown in the updated layout (you'll have to add a new cut between the 2 x 1u caps at the top left, and then make a small bridge over the existing cut - check the layout now to see what I mean). You don't need to use electrolytics, poly caps or whatever will be fine, I've just used the electro symbol because it's only a 2 row span.

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  3. Funky town! Well probed Mirosol, well adjusted Mark! Once my little critter (I should say "if") has his afternoon nap, I'll be tucking straight back into this badboy! Thanks guys, good work!! :0)

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  4. Ah, praise the lord! I was about to "Vince" it, pulling my hair trying to de-bug, then I noticed the trace cut at C9! TFFT! Just one/two questions if I may please, the 1K trimmer on the schem looks to me like it joins lugs 2&3 & not 1&2. Am I reading that wrong, does it matter or not?

    Anyhoo, sounds the tits, me likey & it's got volume in abundance. Bias it right & it doubles up as Escobedo's Jawari!

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    1. The way the trimmer is wired just means that it is "in reverse", but as it is a trimmer, that doesn't really matter. It operates exactly the same either way. If you're bothered by it, just flip the trimmer around 180 degrees :)

      Didn't get to rebuild it myself yet though.. I'm heading out for a few days and prolly get this done too before i leave. The current build has been worked so hard, that i don't plan to save it as is anyway..
      +m

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    2. Haha Milkit...I've been really good lately and have a good run of success..I'll be attacking the 'Riot' again soon so I wont be holding my breath!

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    3. See! attempted the riot again... nothing, straight in the bin. Not touching that effing thing again!

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    4. Tee-hee-hee! What are ya like dude? ;0)

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  5. Cheers dude. Nah I left it as is, but I linked the trimmer via a spst switch, just for added headache during the "shoe-horning" process! Probably a tad unnecessary but...

    Ready to be given the big 'V' tag is this one!

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    1. Nice one Matt, getting towards 250 now! :o)

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  6. Sweet! Where to next, is there much left to cover layout wise?

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    1. :)

      I just don't seem to get myself rebuilding this one.. Maybe i'll whoop up one of those LM386-based drives tonight...
      +m

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  7. can i use a 25K log instead of the 20K log pot? and if so, should i change the resistor value going to pin 3 on the pot?

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    1. Just use the 25K. Whether you use that or the 20K, in the extreme CW position it will connect the 2K2 to ground and so increasing that resistor will alter the maximum mids level. Increasing the pot value puts more resistance between the resistor and ground at the other end of the rotation and so I expect you would get slightly more scoop in the CCW position.

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  8. This comment has been removed by the author.

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    1. you don't need one. this uses NPN transistors.

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  9. Can you do a charge pump with this to make it daisy chain?

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    1. again you don't need a charge pump. this already has the ability to be daisy chained. the only time you NEED a charge pump to daisy change an effect is if the transistors are PNP. ALL effects that use NPN transistors can be daisy chained.

      if you want to use a charge pump to increase the voltage to 18V, i don't see why not, as long as all your electrolytics are rated above that.

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    2. My mistake. I was confusing this with the MI Neo Fuzz (the germ version of this). I have the Neo fuzz and can't get a charge pump to work with it. I tried a DC/DC isolator which worked but was super noisy.

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    3. it might not be the charge pump you made, it could be the power supply has little to no filtering, or there's a lot of noise due to the lights or other devices in the room/on the same power line. next time, instead of posting the same question again after someone answers it, try to clarify what you're asking so someone can try to help.

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  10. Double post mistake. I'm full of mistakes today

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    1. lol. it happens to the best of us. don't think i'm coming down on your or anything, it's hard to convey tone when typing man. trust me, everyone here is here to help.

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  11. Kill 'em with emoticons my mother always said :)

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  12. I shall nominate myself for the February 2016 dipstick of the month award for missing off a component completely, no wonder it didn't work when I first tried it :o/

    Glad I bothered to check though, don't think I found a single bad sound with this build so far, plenty of fuzz on tap, the body and tone controls work nice and smoothly, no unusable extremes, didn't really find much use for the load pot but may well turn out to be a godsend with some guitars, reacts nicely to playing dynamics, cleans up pretty well from the the guitar volume control though never completely clean it's always at least a bit gritty, but it is a fuzz after all!

    Only control not mentioned so far is bias, works just as expected and is very interactive with the other controls, and very easy to find a point where it does varying degrees of that spluttery voltage starved 'crapping out' on notes thing. Only (Fairly minor) issue I have with it is that no matter what settings I tried it would always cut out completely by at most somewhere around 3/4 travel.

    Very happy with this one and definitely getting boxed, just have to fine tune the exact transistors I like best :o)

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