MOSFET Fuzz/Distortion Circuit PUBLIC

Fuzz circuit using CMOS op-amps and discrete MOSFETs.

A high-gain 4-voiced fuzz and distortion circuit using a dual DMOS op-amp IC for making distortion, and several dual discrete MOSFET ICs for generating two different fuzz sounds. Controls Include: Input Gain, Input Level, Driver Gain, Drive, Fuzz 1 enable switch, Fuzz1 symmetry switches (two, with 2 settings each), Fuzz 1 Depth, Bass, Treble, Fuzz 2 enable switch, Fuzz 2 symmetry switches (two, with 2 settings each), Fuzz 2 Depth, and Volume. With all controls at 50%, frequency range above 0 dBV is from 85 Hz to 16 kHz; ideal for 6-string electric guitar, with emphasis on mids and highs between 400 Hz and 4 kHz. With all controls at 100%, range extends from 38 Hz to > 20 kHz. [Not suitable for 7/8-string guitar or bass-guitar.] Maximum gain = +32.3 dBV @ 1.6 kHz with all controls at 50%, or +58.2 dBV @ 1 kHz with all controls at 100%. Distortion is obtained by overdriving the op-amps of IC1. If the input signal is not sufficient to overdrive IC1a, it has enough gain to overdrive IC2b. This therefore is CMOS distortion, known to be tube-like in character. Fuzz is from discrete MOSFETs configured to work like diodes. There are two MOSFET arrays, one hard-clipping (shunt type) and one soft-clipping (feedback type), each with two symmetry switches that set the harmonic content of their respective fuzz sounds. Note that neither MOSFET array, using dual MOSFET devices, affects gain in a perceptible manner, but should affect the sound by clipping the signal, thus imposing fuzz sounds. MOSFET fuzz is also reported to be tube-like in nature. IC6 is specified as a dual BJT op-amp IC that has a reputation for sounding more like a 12AX7 dual-triode preamp tube than any other dual op-amp IC, when overdriven. However, the entire circuit will be a bit noisy, even without Fuzz effects enabled. Power-supply not shown. Requires a dual-polarity DC supply providing +-9VDC or +-12VDC or +-15VDC at >=50 mA of current. And while simulator verified, treat the project as experimental. That is, thoroughly breadborad test it before committing to a solderd build. Also, house the project in a grounded metal rackmount enclosure, to prevent EMF interference.