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MXR M81 distortion issue

Discussion in 'Effects [BG]' started by fermata, Dec 17, 2017.

  1. fermata


    Nov 10, 2015
    Mountain West
    My MXR M81 preamp has developed an issue where the output (both when the pedal is on and when it's off, but not in true bypass mode) is weak and distorted. In the morning it was fine, but in the afternoon it wasn't. I've switched batteries and plugged it into external power, but that didn't resolve it. Any ideas for what might be causing this problem? (And unfortunately, I'm not under warranty.)
  2. boomertech

    boomertech Frank Appleton Commercial User

    Apr 8, 2009
    Syracuse, NY
    Designer/Owner of FEA Labs
    It sounds like the pedal may need a repair. Sounds like an opamp or some other active device (charge pump) may have died.

    I've read that the MXR Constant Headroom Technologyâ„¢ is a charge pump that increases the internal operating voltage for the circuit.

    basscapes and fermata like this.

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