Tribute to Craig Anderton 10: SVF Tone PUBLIC

State Variable Filter Used As 3-Band Tone-Control Circuit with Variable Boosted Center and 2-Voice Resonance

Based on Craig Anderton's "Super Tone Control" project from his book Electronic Projects for Musicians (1980 edition, p140, Amsco Publications). A state variable filter circuit where the high-pass filter is for Treble, the bandpass filter is for Mids, and the low-pass filter is for Bass. There is also a Resonance control (using positive feedback) with a Hi-Lo tone selector-switch. Controls Include: Resonance Tone Switch (Hi or Lo), Resonance, Treble, Mid, Bass, and Center. No volume control. Anderton gives the frequency range of 50 Hz to 15 kHz, but the CircuitLab response curve shows the lows going subsonic (0.0 dBV @ 2.5 Hz) with highs down by -3 dBV @ 15 kHz. There is also a +18.6 dBV peak at 1.6 kHz, with all controls at 50%, mitigated by the Center control (which shifts the peak higher or lower) and the Mid control (which affects the amplitude of the peak). And while originally intended for 6-string guitar, the circuit should work for 6/7/8-string guitars or 4/5/6-string bass. And though simulator verified, treat the circuit as experimental. Fully breadboard test before committing to a soldered build. House in a grounded metal enclosure.