1980 MXR Micro Amp

Model Description:

Made in Rochester, New York, U.S.A., the MXR Innovations Micro Amp is a clean boost pre‑amplifier providing up to a significant 26dB of signal gain. The principle of the MXR Micro Amp (model MX‑133) is to (over)drive the input stage of an amplifier without overly colouring the tone, thereby obviating the need for a tone control. While the simple analogue circuit can simply be used to increase volume, it can also push valve amps into natural saturation and compression. The Micro Amp only came in ‘block’ logo form with no LED or DC input, making it about as simple a stomp box as you can get. MXR went bust in 1984 but the MXR brand was later picked up by Dunlop Manufacturing, who re‑released the Micro Amp, which is essentially the same but with a few more user‑friendly features and manufactured in the Far East. Strangely, at the time, there weren’t that many alternatives to the Micro Amp other than from the Electro‑Harmonix Linear Power Booster (LPB). Clean boosters by their nature are not very ‘sexy’ like some other more in‑your‑face effects, so vintage prices for the Micro Amp remain reasonably affordable.

Pedal Description:

Sometimes less is more and this rugged little white MXR Micro Amp is a case in point. This neat little box, which is surprisingly heavy for its size, provides a flexible amount of volume/gain suitable for overdriving an amp or just boosting clean volume. The Micro Amp is essentially a simple active pre‑amp and does exactly what it says on the tin. This all‑original example from 1980 is in very good condition with only a few minor paint chips – it is a stomp box after all. It also works perfectly with no scratchy pots and, unsurprisingly, only a little hum when on full gain. The circuit isn’t intended to colour the tone and it doesn’t as far as I can tell, meaning that the essential blend of guitar and amp tone is retained. There is not a lot to it but what it does, it does very well. The Micro Amp is good for adding that extra kick you may want for solos or for pushing a valve amp into natural overdrive. It can also push an already distorting valve amp into warm compression without adding too much additional volume, thereby fattening up the tone. Perhaps not an essential pedalboard item but a useful one nevertheless. Just turn it up!


  • Made in Rochester, New York, U.S.A.
  • The ‘Gain’ knob controls the amount of gain – from 0dB to +26dB
  • Standard footswitch turns the effect on and off
  • Standard ¼” input and output mono jack sockets
  • ‘Block’ MXR logo
  • Matching ‘block’ logo baseplate with original screws
  • No LED status indicator or DC power supply input, 9V battery only
  • Original 12‑page instruction manual (but no box/warranty card)

Detail Gallery:

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