PedalBuilder
Well-known member
Picking a favorite fuzz pedal is like picking your favorite offspring. With that said, the Rotobone is a strong candidate for my favorite fuzz. Enough has been written elsewhere about its trumpet-like tones, the glassy cleans when you roll back the volume knob, and its wide range of more traditional fuzz tones, so I won't reprise that here.
At its heart, the circuit is a derivative of the Jordan Bosstone with the PNP transistor installed backwards, with emitter to ground. This softens the distortion and keeps the oscillations that are responsible for the trumpet-like tones from getting too chaotic and unmusical. You could probably use a very low hFE transistor, like certain power transistors, installed with collector to ground to get the same effect, but I haven't tried that myself. Additionally, the Rotobone adds an array of switches: switches to choose between germanium and silicon for both transistors, a low/high gain switch to add/remove an emitter resistor to Q1, and rotary switches for the input and output capacitors.
I made a few changes to mine. The original Rotobone used 1P6T rotary switches for the input and output capacitors. I used 1P8T rotary switches, and added C7, C8, C16, and C17. I also added R2 because I am a firm believer that a fuzz pedal should only have one control that mutes it.*
For this build, I followed the schematic (at the bottom of the post) more or less exactly, with the exception of the transistor selection:
Q1: Central Semiconductor 2N5088, hFE 460
Q2: General Instrument 2N1304, hFE 123, leakage 10µA
Q3: ON Semiconductor 2N4403, hFE 186
Q4: Texas Instruments 182505 (2N404A equivalent), hFE 178, leakage 45µA
The enclosure is a Tayda Ball Silver 1590BB2, so I am holding my breath and waiting for it to spontaneously cover itself with scratches. I used one in this build because I figured that the inevitable patina would go well with the overall aesthetic of the pedal. I made a small error on the UV print—the Ge/Si switches have Ge and Si backwards, but otherwise everything came out exactly as planned.
Inside
Outside
*Unless the pedal is a Buzzaround or Dizzy Tone and you're adding a traditional volume knob.
At its heart, the circuit is a derivative of the Jordan Bosstone with the PNP transistor installed backwards, with emitter to ground. This softens the distortion and keeps the oscillations that are responsible for the trumpet-like tones from getting too chaotic and unmusical. You could probably use a very low hFE transistor, like certain power transistors, installed with collector to ground to get the same effect, but I haven't tried that myself. Additionally, the Rotobone adds an array of switches: switches to choose between germanium and silicon for both transistors, a low/high gain switch to add/remove an emitter resistor to Q1, and rotary switches for the input and output capacitors.
I made a few changes to mine. The original Rotobone used 1P6T rotary switches for the input and output capacitors. I used 1P8T rotary switches, and added C7, C8, C16, and C17. I also added R2 because I am a firm believer that a fuzz pedal should only have one control that mutes it.*
For this build, I followed the schematic (at the bottom of the post) more or less exactly, with the exception of the transistor selection:
Q1: Central Semiconductor 2N5088, hFE 460
Q2: General Instrument 2N1304, hFE 123, leakage 10µA
Q3: ON Semiconductor 2N4403, hFE 186
Q4: Texas Instruments 182505 (2N404A equivalent), hFE 178, leakage 45µA
The enclosure is a Tayda Ball Silver 1590BB2, so I am holding my breath and waiting for it to spontaneously cover itself with scratches. I used one in this build because I figured that the inevitable patina would go well with the overall aesthetic of the pedal. I made a small error on the UV print—the Ge/Si switches have Ge and Si backwards, but otherwise everything came out exactly as planned.
Inside
Outside
