A couple years ago, inspired by some questionably accurate reports that Dan Auerbach used a Maestro MFZ-1 as his main fuzz on the early Black Keys albums, I decided to build my own. Unfortunately, it sounded truly awful. Lots of noise, not a ton of fuzz, and very muddy. It was the worst sounding pedal that I've ever owned—and I used to own a Metal Zone.
But I liked the enclosure and felt bad that it was housing something that I'd never use, so I spent some time brainstorming about how to repurpose the enclosure. I had already built most of the other circuits that would be a thematically appropriate match (e.g.
Rosac Nu-Fuzz,
Shin-ei Companion), and didn't want to have to add the extra unlabeled holes required to adapt it to a Standard Fuzz or Hoof. At the same time, I was breadboarding Marshall Supa Fuzz, a Tone Bender Mk. II with a couple changes to component values. In a stroke of good luck, my research on the Supa Fuzz unearthed an article that claimed that Auerbach used a Supa Fuzz on several albums. I tried a variety of transistor combinations, and settled on some transistor specs that are close to those described by
Lucifer's Trip on the DIY Stompboxes forum:
Q1: hFE 230, leakage 125µA
Q2: hFE 275, leakage 190µA
Q3: hFE 230, leakage 125µA
Collector voltages (VCC = 9.2v, ambient temperature 72ºF):
Q1C: 9.11v
Q2C: 0.24v
Q3C: 7.86v
The transistors are NPN germaniums from Texas Instruments, house parts labeled N-149. As far as I can tell, they're the same thing as 2N1308, with the same gain and leakage range.
I made a slight tweak to the power section, adding a ferrite bead and series resistor. Those added parts cut down on a lot of the noise that the pedal had on the breadboard. I suspect that putting the pedal in a grounded aluminum enclosure would have had the same effect, but adding them was easy and helped make the layout look more symmetrical. I'm a sucker for symmetry in PCBs and am not above adding components for largely aesthetic reasons.
Satisfied with the sound of the breadboard, I put together a PCB specifically for the components and sent it off to JLCPCB for fabrication. A week or so later the PCBs arrived and I built the pedal. I'm quite happy with the sound. It's basically an angrier Tone Bender Mk. II that's on the verge of self-oscillation. Does it sound like the Black Keys? Not one bit. It sounds more like Sleep, and it definitely dooms. So while it's not a particularly good match for the enclosure, it was a fun build and sounds great.
