StarMan 1: Basic Op-Amp Distortion PUBLIC

Basic Op-Amp Distortion for Guitar, with 2-Band Tone.

Basic op-amp distortion circuit for guitar with 2-band James-style tone-control. Uses one dual JFET-input op-amp to provide gain and active tone. Distortion is obtained by using the Input Stage to overdrive the Output Stage. Controls Include: Gain, Drive, Bass, Treble, and Volume. If more distortion is desired, use 1M for Gain pot. For less distortion, use 250k. Frequency Range 13 Hz to 10 kHz with all controls at 50%, but bandwidth increases with controls set > 50%. Suitable for 6/7/8-string guitar or 4/5/6-string bass, and for stomp-box or rackmount projects. Example Gains are +21 dBV @ 100 Hz and +18 dBV @ 1 kHz with all controls at 50%, or at least twice that with controls at 100%. The Treble control boosts/cuts by +-3 dBV, while the Bass control boosts/cuts by +-5 dBV. Midrange is fixed. Power-supply not shown. Requires a regulated dual-polarity DC supply providing +-9VDC or +-12VDC or +-15VDC at >= 20 mA of current. Note: Higher supply voltage results in less op-amp noise but makes op-amp harder to overdrive. For Clean Boost instead of Distortion, substitute an OPA2134PA for the TL082CP. For MOSFET distortion instead of JFET distortion, substitute an OPA2156IDR. For BJT distortion similar to that of a 12AX7 preamp tube, substitute an NJM5532M. And though simulator verified, treat the circuit as experimental. Breadboard test before committing to a soldered build. House in a grounded metal enclosure.