mdc
Well-known member
Here's a very straightforward MOSFET bass fuzz I've been messing around with on ye olde breadboard for the past week or two for the bass player in my band.
SHO —>the bass half of a James tone stack—>MOSFET fuzz face
The 'fuzz' adjustment comes via the SHO's crackle pot, with a heavy amount of attenuation from the EQ stage. The 'bass' control can also serve as an extra gain stage depending on where the fuzz is set. Flat EQ is around 10:00, after that you get a bass boost which will very quickly overload the fuzz face and create and extremely wooly/synth-y blown out fuzz.
Great cleanup from the volume knob, doesn't seem to freak out with buffers in front of it.
For the fuzz face stage, I started with Escobedo's many faces of fuzz and basically fuzz-factory'd it, adding a bunch of trim pots wherever it seemed like they might be useful. Tweaked, measured, tweaked some more. You could certainly replace a lot of resistors with pots if you so chose and get weird, but I went utilitarian with it.
Vero is vero-fied:
Voltages seem pretty forgiving, the SHO should be normal (~7V at min crackle, ~4.5V at max); Q3 drain should be north of 4V but I honestly didn't hear much difference once it got above 4V or so. R11 (5K6) could easily be swapped for a trimmer or an external pot or both; you might need to swap it for a different value if Q3 is giving you a lower reading than you'd like to see (I had a 4K7 on the breadboard but with the power filtering added, I needed to raise the resistor to 5K6 after I built it up).
Caveat - If you don't like MOSFET-based circuits, you probably won't like this. It has a distinctive, chewy kind of fuzz that I really, really like. I haven't boxed it yet, but it seems relatively quiet for a fuzz face all things considered. I a/b'd it with a sputnik III and it has more gain/fuzz on tap, more top end, and only marginally more noise - even with the mess of spaghetti wires and alligator clips that are attaching the vero to the breadboard to the test box.
Anyway! If you have some BS170s around, this is a quick and easy build with lots of room for mods. I'll post some photos after I box it up this eve.
SHO —>the bass half of a James tone stack—>MOSFET fuzz face
The 'fuzz' adjustment comes via the SHO's crackle pot, with a heavy amount of attenuation from the EQ stage. The 'bass' control can also serve as an extra gain stage depending on where the fuzz is set. Flat EQ is around 10:00, after that you get a bass boost which will very quickly overload the fuzz face and create and extremely wooly/synth-y blown out fuzz.
Great cleanup from the volume knob, doesn't seem to freak out with buffers in front of it.
For the fuzz face stage, I started with Escobedo's many faces of fuzz and basically fuzz-factory'd it, adding a bunch of trim pots wherever it seemed like they might be useful. Tweaked, measured, tweaked some more. You could certainly replace a lot of resistors with pots if you so chose and get weird, but I went utilitarian with it.
Vero is vero-fied:
Voltages seem pretty forgiving, the SHO should be normal (~7V at min crackle, ~4.5V at max); Q3 drain should be north of 4V but I honestly didn't hear much difference once it got above 4V or so. R11 (5K6) could easily be swapped for a trimmer or an external pot or both; you might need to swap it for a different value if Q3 is giving you a lower reading than you'd like to see (I had a 4K7 on the breadboard but with the power filtering added, I needed to raise the resistor to 5K6 after I built it up).
Caveat - If you don't like MOSFET-based circuits, you probably won't like this. It has a distinctive, chewy kind of fuzz that I really, really like. I haven't boxed it yet, but it seems relatively quiet for a fuzz face all things considered. I a/b'd it with a sputnik III and it has more gain/fuzz on tap, more top end, and only marginally more noise - even with the mess of spaghetti wires and alligator clips that are attaching the vero to the breadboard to the test box.
Anyway! If you have some BS170s around, this is a quick and easy build with lots of room for mods. I'll post some photos after I box it up this eve.
