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.



15 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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