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MXR M66S Classic Overdrive Guitar Effects Pedal  

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MXR's GCM66 Classic Overdrive makes sound simple, adding sustain and gain without coloring your guitar or amp's tone and is housed in an indestructible die-cast housing. It can be powered by one 9-vol... Click To Read More About This Product

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MXR's GCM66 Classic Overdrive makes sound simple, adding sustain and gain without coloring your guitar or amp's tone and is housed in an indestructible die-cast housing. It can be powered by one 9-volt battery (sold separately) or Dunlop ECB003 AC adapter (sold separately).

  • Output and gain controls for ultimate control at any volume
  • Simple footswitch toggles effect on or bypass
All pedals - one year parts and labor warranty.

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Review Snapshot

by PowerReviews
MXRM66S Classic Overdrive Guitar Effects Pedal

(based on 1 review)

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Reviewed by 1 customer

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Excellent as a drive or clean boost with 2 modes

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By Thunderstruck507

from Fayetteville, AR

About Me Experienced


  • Excellent Sound Quality
  • Hidden Mode Switch
  • No Signal Noise
  • Responsive
  • Retains Low End
  • Sturdy Construction
  • Versatile


    Best Uses

    • Amateur Recording
    • Events
    • Home Studio
    • Performances

    Comments about MXR M66S Classic Overdrive Guitar Effects Pedal:

    This is an excellent overdrive. I was really looking at a Maxon 808 and a few other popular overdrives to use as a clean boost (0 gain, max output volume, feeding the distorted channel of a tube amp) for metal playing to tighten up the sound. This pedal works perfect for that. Unlike a lot of OD I've tried it retains the low end and the tone of the guitar/amp and just tightens up the flab, makes the sound crisp, and really gives bite and sustain.

    Google and you will find it has a hidden switch on the board inside to change from the MXR GT-OD sound to a Zakk Wylde Signature Overdrive sound. Both sound excellent but one offers more volume and bass frequencies on my Marshall DSL401 (feeding a 4x12 Bugera cabinet).

    I drilled a hole in the cover of the pedal so I can flip the switch with a screwdriver.

    This pedal has 0 signal noise and when it's off it sounds exactly like there is no pedal in the chain at all so the bypass is extremely good unlike other pedals I've tried.

    On the clean channel it works well as a clean boost but if you dial up the gain it gives a very warm and bluesy overdrive tone that fills the gap well between my clean and OD1 channel.

    On the low gain overdrive channel it gives a nice crispness and bite and boosts sustain and attack for better hammer ons and pull offs without adding more distortion/gain to the sound.

    On the high gain overdrive channel it just cleans everything up and takes the muddiness out, especially in Drop D or Drop C tunings.

    Used these are the best value on the market for an overdrive.

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