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Onboard active tone controls

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  • Onboard active tone controls

    Can anyone point me in the direction of theory or schematics for guitar onboard active tone controls similar to the EMG-EXG or EMG-SPC. I'm not actually trying to clone these devices, but rather want to play with circuits that do something similar that I can choose my own frequency boost and cut.

    The EXG is flat with the knob all the way down, and at full up boosts both treble and bass while cutting mids. The resulting curve looks a lot like the response you might see for a Fender tone stack.

    The SPC does sort of the opposite, flat when turned down, and boosts the mids and rolls off treble when turned up.

    What I sort of envision is something like a mini tonestack with trimmers driven by an opamp (maybe dual opamp for drive and recovery?), with a single knob for blending between full tonestack and full bypass.

    Of course, it doesn't have to be opamp based, a circuit using jfets or tubes would be even nicer.

  • #2
    Never mind, my brain apparently takes Mondays off.

    The control, say 100k pot would blend between the original input and two inverting gain stages with a tone network in between. Output comes off the wiper.