Modified Blues Breaker Circuit PUBLIC

Highly-Modified Marshall "Blues Breaker" Overdrive Circuit

Highly-modified Marshall "Blues Breaker" Overdrive circuit. Controls Include: Gain, fuzz Symmetry switches, tone Center, Drive, Bass, Mid, Treble, and Master. Modifications: Changes in some part-values (to reshape frequency response curve), use of Schottky diodes (to get softer fuzz) and different diode-matrix topology (to provide 3 choices of fuzz voicing), additional passive filtering (to reshape frequency response curve), addition of active 3-band tone-control circuit using extra op-amp, addition of gain stage at the output using another extra op-amp, and use of upgraded op-amps (to reduce noise). Frequency range between low and high -3 dBV corners is from 18 Hz to 2 kHz with all controls at 50%. Suitable for 6/7/8-string guitar and 4/5/6-string bass, with emphasis on lows and mids. However, increase in overall gain by setting controls > 50% results in extension of high frequency limit. Maximum gain = +15.3 dBV (Vo/Vi = 5.8) @ 630 Hz with all controls at 50%, or "+87 dBV (Vo/Vi = 22,387) @ 630 Hz with all controls at 100%, thus placing the circuit in the high-gain overdrive category with controls set > 50%. Caution! Do not use the circuit with all controls at 100% except briefly as a worst-case test while breadboarding. The circuit can be used for a stomp-box or rackmount application, and the battery can be replaced by a regulated single-polarity +9VDC supply providing >= 40 mA of current, but include the +4.5VDC tap, as shown. And while simulator verified, treat the circuit as experimental. Breadboard test it before committing it to a soldered build.