RO Guitar Preamp 7: Boost with Fuzz PUBLIC

Richter Original Guitar Preamp 7: Booster with Diode Fuzz

Richter Original guitar preamp, version 7; clean boost with feedback-type Schottky-diode array for fuzz. Controls Include: Input Level, Gain, Fuzz enable switch, Fuzz symmetry switches, Fuzz Depth, Drive, Bass, Treble, Trim, and Volume. Specified IC is the OPA2134PA dual FET-input op-amp IC, chosen to ensure clean op-amp operation without fuzz. For overdriven op-amp distortion in addition to diode fuzz, consider the following substitutions. For JEFT fuzz, use the TL082CP. For MOSFET fuzz, use the OPA2156IDR. For tube-like BJT fuzz, use the NJM5532M (the Japanese version of the NE5532N). [Note: Each substitution will involve increased noise. Conduct listening-test with desired IC while breadboarding to determine if noise is an issue.] Hint: Fuzz cuts overall gain significantly, depending on setting of Fuzz Depth control. The symmetry switches set harmonic content of the fuzz. Frequency Range 22 Hz to 5.6 kHz with all controls at 50% but no fuzz, or 5 Hz to 20 kHz with all controls at 100% but no fuzz, or 10 Hz to 10 kHz with all controls at 100% and full fuzz. Suitable for 6/7/8-string guitar or 4/5/6-string bass. Maximum Gain = +20 dBV between 250 Hz and 400 Hz with all controls at 50%, or +57.5 dBV with all controls at 100% but no fuzz, or +38 dBV with all controls at 100% and full fuzz. Power-supply not shown. Requires a regulated dual-polarity DC supply providing +-9VDC or +-12VDC or +-15 VDC @ >= 25 mA of current. [Note: Higher supply voltage results in lower op-amp noise.] And though simulator verified, treat the circuit as experimental. Breadboard test before committing to a soldered build. House project in a grounded metal enclosure.