7-Band Tone for Guitar PUBLIC

7-Band Active Tone-Control Circuit for Guitar or Bass

7-band passive tone-stack with op-amp boost before and after the stack. Controls Include: Input Gain, Drive, 7 tone pots, Output Gain, and Volume. Tone pots are labeled for center frequencies of passbands. Each tone pot has an adjustment range of only +-6 dBV; meaning, +3 dBV boost or -3 dBV cut if going by center position as corresponding to 0 dBV. However, due to op-amp boosting, the whole circuit provides gain > +20 dBV when all controls are at 50%. Consequently, this circuit can be considered a Clean Boost with 7-Band Tone. The specified op-amps were chosen to ensure clean operation of the circuit. However, should overdriven op-amp distortion be desired, IC1 must remain an OPA2134PA but IC2 can be replaced by one of the following. The OPA2156IDR dual CMOS op-amp IC will give tube-like distortion due to having MOSFET input stages, while the NM5532M (Japanese version of NE5532N) dual BJT op-amp IC is said to sound more like a 12AX7 preamp tube than any other dual op-amp IC. But in both cases, noise will be a factor. Breadboard testing will reveal if noise levels are unacceptable when making such substitutions. And if substitution are made for that purpose, the circuit can be called "Distortion w. 7-Band Tone", and Gain control values can be increased to get more intense distortion from the circuit. Power-supply not shown. Requires a regulated dual-polarity DC supply providing +-9VDC or +-12VDC or +-15VDC at >= 40 mA of current. Note: Higher supply voltages result in lower op-amp noise, but makes them harder to overdrive. And while the circuit is simulator verified, treat it as experimental. Breadboard test it before committing to a soldered build. And house in a grounded metal enclosure.