This is a library of perfboard and single-sided PCB effect layouts for guitar and bass. I'm not an electrical engineer by any stretch of the imagination, just a DIY'er who likes drawing layouts. It is meant for the hobbyist (so commercial use of any of these layout is not allowed without permission) and as a way to give back to the online DIY community.

Friday, April 14, 2017

Spaceman Effects Gemini III Dual Fuzz Generator

This week's Fuzz Friday layout happens to be the 500th layout on the blog! So for #500 it has to be something cool, so here's a really unique fuzz from Spaceman Effects–the Gemini III Dual Fuzz Generator. As the name implies, it has 2 sides: silicon and germanium. The Blend knob pans between the 2, and each side has a 3-way gain switch. I've laid it out for board mounted pots for a 125B with top mounted jacks.

It's a good idea to experiment with the transistors, especially on the germanium side. Here's some good alternatives from digi2t who traced it over on DIYSB:

Q1: Russian MP20B (hFE: 80-85)
Q2: Russian GT404 (hFE: 120-130)
Q3: Russian GT402 (hFE: 100-115)
Q5: BC109B or 2N3700 (hFE: mid 200s)
Q7: 2N5088

Also the 1nF cap near the input apparently really needs to be a polystyrene. YMMV


  1. Replies
    1. No. See the hFE ranges listed below the layout image.

  2. Hi!

    1. Congrats on youknowwhat!
    2. What is the point of using only one transformer winding? Seems to me like a bizarre method of using transformer as a choke.

    1. 1. Thanks!
      2. I have no idea. I don't design 'em, I just lay 'em out. :D

      (But I thought that was odd too lol)

    2. 2. Oh, sorry, I know. I was just wondering if anyone (you in particular) knows what's wrong with this pedal, lol :D

    3. Look up 'pickup simulator schematic' on Google. The reason they use these audio transformers, is because (I think) they're fairly easy to find, cheapish, and generally more in spec or something?

      Also: from an AMZ article - "This circuit may be used to add a frequency response before any circuit that will benefit from an input that emulates a guitar pickup. It can add a bit of enhanced high frequency response in addition to converting the signal impedance. "

    4. Hi, Charles,

      Thanks, I see now. It's weird, but reasonable. I first thought of using an unductance with the same properties as the transformer's primary coil, but could not find one that is more compact cheaper and easily obtainable then 42tm series itself. Even more, i could not find one that has similar active impedance.
      I need more research...

  3. 308k isn't a standard resistor value. I'm guessing 309k is close enough, though.