Tuesday, 29 January 2013

ETI Fuzz Struzz (a.k.a. Guitar Effects Unit)

There was a mistake on the layout, that's now fixed. This calls for both +9V and -9V supply. Use of inverter pump daughter board is recommended.

The GEU is good sounding octave fuzz, with an optional mode of just fuzz. The fuzz is a fully rectified signal and is quite chewy. For some the Fuzz alone might not be loud enough, this can be fixed by raising the value of the 820 ohm resistor and lowering the 39k one. Or one could just replace both with a normal volume pot for a more standard approach. The "struzz" is the fuzz with an octave higher signal mixed in. Good for singal notes and leads.



17 comments:

  1. just a question but can you please double click you vero board and check the "draw coordinates" box... would be super helpful.

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    1. I could do that.. But it's abcd.. on horizontal and abcd.. on vertical. That's pretty confusing. Plus none of Mark's veros have those and i'm trying to keep some uniformity.
      +m

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  2. aaand just built.

    no bueno.

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  3. weird, it's not good? i built this on pcb, and with a few mods it was a really nice box, very versatile!

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    1. I'm guessing that the build doesn't work... I'll take a look at it soonish.
      +m

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  4. I've just built this and at the moment it doesn't work, I think I've spotted the problem though, the schem show that it uses two batteries and has a +9v and a -9v supply. It looks like it's missing the -9v supply which, according to this post anyway, should go to pin 4. I guess this mean it'll need a bit of rejigging as currently a lot of stuff going to ground is going through that pin.

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    1. I have no idea how i missed that. As usual you're correct...

      I could fix it, but other option would be to scrap it. Mainly because +/- circuits are a pain. Maybe i'll just fix it...
      +m

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    2. And fixed. It took some rejiggin, but you should be able to fix it with coulple of link wires..
      +m

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    3. Thanks dude, I would have looked at this earlier but I had friends round last night. I've made the changes to my board to reflect your changes and it now works but it's extremely quiet and a little thin sounding, I think the layout's correct though, I've probably just popped an incorrect resistor value in somewhere. Time for a little digging.

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    4. OK, so it turns out I just need to start learning how to read properly. I used 1nf caps instead of 1uf, D'oh. This is the first Octave-Fuzz I've built so I've not really got much to compare it to but it sounds pretty good, the fuzz is nice and thick and you can get a fairly decent octave up sound with the neck pickup and the fuzz pot rolled back. The only problem at the moment is that the 'fuzz only' is very quiet compared to the struzz setting. The schem says that altering the values of the 820r and 39k resistors should fix this so I'll have a play and let you know how it turns out.

      The only differences between my board and the updated layout are that instead of having a separate row for the ground connection I've had to solder a wire to a spare hole in the middle of the board, I kept the old ground connection and used it as -9v and just put an extra cut infront of pin 4 of the IC. The new layout is definitely correct and will work if anyone fancies trying it.

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    5. Let me know how it goes.. If it works, you've broken a magical record :P
      +m

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    6. So it is verified! You've earned yourself a beer!
      +m

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    7. Go team! I think this one would be something you'd like too, in the struzz position with the fuzz rolled right back it's very reminiscent of the Green Ringer. 10k in place of the 39k definitely helps with the volume drop on the fuzz side by the way.

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  5. No way! I built this very box in the late 70's from the design in ETi magazine, and very good it was too! I'm sure I still have the magazine with the PCB design included. You could coax some mad sounds out of it, and it was a simple enough design to modify and circuit bend for some even crazier sounds!

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  6. hi guys,
    i got some bends for this circuit if ya wanna play with 'em.
    the actual schematic is indeed the eti fuzz "struzz"
    i reccomend doing the following
    ditch the 560p cap. ditch the q1 emitter resistor, replace with a jumper.
    use mpsa13 for the transistor
    make the diodes water clear green led's. mind the orientation, this isn't a diode clipper in this config (tho a diode clipper will work kinda) it's a rectifier.
    ditch the 39k/820r voltage divider and replace it with a 50k linear pot. now ya got volume control of the fuzz side.
    ditch the 1k/560r (1k/1k on the schematic) voltage divider for a 1k pot. now you can adjust the volume of the octave side. the sustain will still affect both sides.
    i didn't like the fact that there was no dc blocking cap on the output of this.
    on the circuit board, i just cut the trace between the footswitches and stuck a 470n to bridge it. no dc worries, slightly smoother sound on the output. you could hack it in on this layout on row 4 if ya want to.
    more balls to the fuzz, better drive to the octave side and it will track better and cleaner.
    if you wanna break the node the diodes share and put a switch there to connect/disconnect it, you can get a very kinda cool buzzy farty octave downish kinda thing that will track to about your 12th fret on your high e string. once ya go higher, it will die. if ya strum a low string, you can play again.
    its kinda insane and not worth a switch really, but fun. and it has a huge effect on the octave side. you loose the fundamental cancellation but still get a noticeable amount of the octave effect.
    and for extra fun, ya can mount the led's to the front of the enclosure, they will glow when you play, and will get brighter the harder you play.
    it cleans up a little better too from the guitar.. never gets clean clean, but similar to turning down into a cranked tube amp on the dirt channel. it gets quieter and kinda cleaner, but... not all the way.
    those are my hacks to it. if ya try 'em, let me know.
    peace guys
    pink

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  7. here's a modified schematic and vero layout.
    i haven't built the vero, but it's based on miro's excellent verified layout on tagboard effects. i just took a different approach
    so it has 3 knobs now instead of just one. also included a daughterboard for +/-9v with an 1cl7660. added a pull down resistor on the vero for the fuzz switch, an output cap and a couple limiting resistors so ya don't smoke your pots.

    zmokink yer pots is no good for you. ;)

    i've built this on the old graymark kit boards and its a lot of fun and a fairly easy build. anyways...
    vero

    [img]http://i605.photobucket.com/albums/tt137/pinkjimiphoton/dBfx%20Double%20Hit%201.0%20rough_zpsjkag9xq9.png[/img]

    moddified schematic

    [img]http://i605.photobucket.com/albums/tt137/pinkjimiphoton/dBfx%20Double%20Hit%201.0_zpstuzpluix.jpg[/img]

    this way, you can get the fuzz a little over unity, or turn it down to a useable level. same with the octave side. sustain affects both sides of it still. it sounds pretty good, and the octave part tracks well. if you REALLY want to, you can put a master volume pot on it, but it's just overkill, as ya can set the volume of the fuzz and octave independently.

    if ya build it, have fun. peace!

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