MXR · Micro Amp · 1978–1984 (MXR); reissued by Dunlop as the M133
The Micro Amp is the plainest-looking pedal MXR ever made, a milk-white box with black text and one knob. It came out in 1978 and does one job. An op-amp adds up to 26 dB of clean boost, so you can push an amp harder, even out a quiet guitar against a loud one, or make up for signal lost in a long chain of pedals. It's become one of the most used boost pedals around. Jack White has leaned on one since the White Stripes, and John Frusciante is a fan too. Dunlop still makes it as the M133 with an LED and a power jack, and in 2014 the MXR Custom Shop added the Micro Amp+ with bass and treble knobs and true bypass. Some players find the original a little trebly and noisy, which is what the + set out to fix. A Rochester original is a nice bit of MXR history. If you only want the boost, a working M133 does the same job and turns up everywhere.
Scratchy Gain pots, worn footswitches and broken battery snaps are the usual problems. A little hiss at full gain is normal for the circuit.
Buying guide
For the boost, buy a Dunlop M133 titled tested, like the $74 and $83 delivered ones from US sellers. About 178 are for sale and most ask $80–230 delivered, a wide band because many Japanese resellers ask about $165 to $260 for M133s that go for under $90 in the US. MXR originals from 1978 to 1984 start at $229 for the 1980 block-logo one we'd pick, and units made before 1981 run on a battery only. Ask for a clip turning Gain from zero to full with no crackle, and pass on the $694 1980 unit from Japan, three times the US one.
$73.95est. delivered
The lowest delivered Micro Amp at $74, a Dunlop M133 titled tested and working from a 99.6% US seller.
MXR Micro Amp M133 Boost Guitar Effect Pedal - TESTED AND WORKING
$83.27est. delivered
Another M133 titled tested and working, at $83 delivered from a 100% US seller. That's about half what Japanese resellers ask for the same pedal.
Dunlop MXR Micro Amp M133 Boost Guitar Effect Pedal Tested Working
$73.95est. delivered
Titled tested and working, and the M133 takes a 9V adapter, so it's ready for a pedalboard.
MXR Micro Amp M133 Boost Guitar Effect Pedal - TESTED AND WORKING
$229.00est. delivered
Titled 1980 block logo, a Rochester original, at $229 delivered from a 100% US seller, about a third of the 1980 unit from Japan. A 1980 unit runs on a battery only.
MXR Micro Amp Clean Boost Rare Vintage 1980 Block Logo Guitar Effect Pedal
Delivered prices include shipping as eBay quoted it to a US address on Oct 10, 2026. Many sellers charge by distance, so your total may differ. eBay shows yours before you pay.
Snapshot
Checked . Some may have sold.
Delivered prices include shipping as eBay quoted it to a US address on Oct 10, 2026. Many sellers charge by distance, so your total may differ. eBay shows yours before you pay.
Used$73.95est. delivered
$65.00 + $8.95 shipping
Buy It Now$65.00
Good buy
Dunlop M133, titled tested and working. In the US.
Seller: 456music
99.6% positive
Used$83.27est. delivered
$75.00 + $8.27 shipping
Buy It Now$75.00
This seller takes offers, and many sellers accept less than the asking price.
Fine if you might miss it? Send an offer first. Someone else can still buy it while you wait for a reply.
Want it for sure? Use Buy It Now.
Good buy
Dunlop M133, titled tested and working. In the US.
Seller: miggutri_0
100% positive
Used$229.00est. delivered
$219.00 + $10.00 shipping
Buy It Now$219.00
Good buy
Titled 1980 block logo. Battery only.
Seller: srz_audio
100% positive
Used$125.99est. delivered
$106.99 + $19.00 shipping
Buy It Now$106.99
Our take
With its original box. Ships from Japan.
Seller: turtles5
100% positive
Used$160.96delivered
$160.96 · free shipping
Buy It Now$160.96
Our take
No model or year in the title. Ships from Japan.
Seller: dimeback-516
99.5% positive
Used$209.99est. delivered
$184.99 + $25.00 shipping
Buy It Now$184.99
This seller takes offers, and many sellers accept less than the asking price.
Fine if you might miss it? Send an offer first. Someone else can still buy it while you wait for a reply.
Want it for sure? Use Buy It Now.
Our take
M133 with box, about $125 more than a tested US one. Ships from Japan.
Seller: k5_japan
99.8% positive
Used$75.95delivered
$75.95 · free shipping
Buy It Now$75.95
This seller takes offers, and many sellers accept less than the asking price.
Fine if you might miss it? Send an offer first. Someone else can still buy it while you wait for a reply.
Want it for sure? Use Buy It Now.
Check the seller
Another seller uses the same title. Compare photos before you buy.
Seller: rememberthatcollectibles
100% positive
![MXR 1980 Micro Amp [33-008122]](https://i.ebayimg.com/images/g/-KMAAeSwZsBqj-LP/s-l500.jpg)
Used$694.00delivered
$694.00 · free shipping
Buy It Now$694.00
This seller takes offers, and many sellers accept less than the asking price.
Fine if you might miss it? Send an offer first. Someone else can still buy it while you wait for a reply.
Want it for sure? Use Buy It Now.
Priced high
Titled 1980, about $465 over the band. Ships from Japan.
Seller: ishibashimusic
100% positive
Prices change daily. The live eBay search shows everything listed now, including anything new since Oct 10, 2026.
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