MXR M133 Micro Amp
MXR M133 Micro Amp

M133 Micro Amp, Guitar/Bass booster from MXR.

All user reviews for the MXR M133 Micro Amp

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Average Score:4.8( 4.8/5 based on 33 reviews )
 26 reviews79 %
 5 reviews15 %
Audience: Beginners Value For Money : Excellent
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Fireguy8402's review"Good Clean Boost"

MXR M133 Micro Amp
The MXR Micro Amp M-133 is the most basic pedal you can find. An input from your guitar, an output to your amplifier, a power jack and one volume knob, and that’s it. It’s very similar in structural design to the Phase 90 and it’s the same size: 2 ½” by 4 ½” by 5 ½”. There is a red LED that lets you know when the pedal is engaged and the pedal can be powered by a 9 volt battery or by an additional power supply.


This pedal is a one trick pony, but you are able to use that trick in many different ways. Basically all this pedal does is boosts your signal, and this will do different things depending on where you put it in your signal path. In front of a tube amp this pedal can push you over the edge if the amp is set on the verge of breakup, while retaining your tone. When used in the effects loop of an amp this pedal can provide a huge boost in volume if needed that is much cleaner than when it’s used in front of the amp. This pedal is also handy to match the volume of guitars. For example if you use low output single coils in a Stratocaster and then switch off to a hot rodded Les Paul there will be a change in volume during a gig. Kick this pedal on while you play the Strat and off while you play the LP and you wont have to be constantly changing your volume knob on your amp during the show


This pedal does not suck any noticeable high end off of your tone, so I would say the bypass is very good. This pedal is not an overdrive pedal, but can be used to push an amp into that territory if it’s placed before the input of an amp and it does that while staying clean and true to the tone that you start with. I mostly use this pedal in the effects loop of my amplifiers because I don’t need a change in preamp gain/volume, but I prefer a super clean boost of volume. This pedal works wonders here. What you put into this pedal is what you get out, only at a higher volume. I have experienced no loss of tone or additional noise when used with several different guitars and amps.


Overall I think this is a great pedal to have in your arsenal. It can push the front end of your amp, provide tons of volume boost in the loop, match signals for different guitars during a gig, and regain a quality signal if many pedals are used in succession. It’s built like a brick and it doesn’t take a lot of space on your board. I think it’s a great pedal, and I would suggest it to anyone who would need a boost.

ericthegreat's review"small but powerful"

MXR M133 Micro Amp
This is simply a 7 band equalizer in stomp box skin.
I believe it is all analog.
No, no editing through pc, just 8 mini faders
This is only audio 1/4" connections
and it is not rackable in the traditional sense.


Setup is simple, plug your instrument in one end, the amp on the other and there you go. The sound editing is as simple as bending over and adjusting one of 8 faders. I have never consulted the manual, and never plan to. There is really nothing else to know.


The EQ is pretty good. Its a little noisy, but that is kind of a stupid deal with boss anyways. If you are really serious about EQ, you need a rack mountable, multi band equalizer. I use this on a Rhodes piano, and my Parker guitar. Works pretty good in getting some lows out and boosting highs to cut through the rest of the band for soloing. Works best after a distortion pedal to reduce the &; Like I said before, its a little noisy, I would never use it in a recording session, but in a live setting, no one would ever notice.


I have been using this for three years. I like its easy portability (its so small). I dislike the hiss you get when you boost the highs. This is really the only stomp box EQ I have ever tried. The prices for this pedal are decent. Its worth it if you need a clearer, brighter tone, or if you won't more low end say on a solo. Yeah, I would buy it again, its just so darn easy to use. But I love it, reproduce the sound of the amp by inflating the sound and giving it more body and thickness. You wont want to go with out this pedal if you can get your hands on one.

ejendres's review"cool pedal"

MXR M133 Micro Amp
This is a clean boost pedal. I believe its all analog, but I'm not positive. It is the most simple a pedal can be, an on/off switch and a gain knob.


This pedal works exactly as advertised. It boosts the signal. Super easy to setup and use, considering its only one knob. I never needed to consult the manual so I can not comment on it.


This is designed to be a boost for leads or to help compensate between pickup outputs when switching between guitars. When you have your amp set for cleans or low to mid gain it works beautifully. There is a very distinct jump in volume with out any real coloring of your tone.

However, as you increase the amp gain the less effective this pedal is. With as the pre amp gain increases the pedal adds less and less volume. After a while it mostly just adds punch and saturation. Which is a very cool sound in its own right. It comes in really handy if you have an amp that need just a little extra push to get it into high gain territory.


If you're a clean to mid gain player looking for a volume boost this is the pedal for you. It can do significant boosts in volume without really touching your tone. Which is the entire point of a clean boost.

If you're a high gain player looking for a volume boost you should look else where. The jump in volume even with the gain all the way up on the pedal isn't significant enough to be useful. However, if your a high gain player looking for a way to add saturation and punch while retaining your core tone, definitely try a microamp out. It may be just what you're looking for.

moosers's review

MXR M133 Micro Amp
The MXR M133 Micro Amp is a boost pedal, designed for use with electric guitar.  The pedal is an analog one, with 1/4 inch connections for both input and output.  The pedal is powered with 9 volts, and isn't rack mountable as it is a foot pedal.


The make up of the MXR M133 Micro Amp is just about as simple as it can get for any pedal.  All that there is is a knob for gain!  Simply set your level to get different types of boosting, and you're good to go.  That's all that there is to the pedal, period, so a manual definitely isn't needed at all.


As far as boost pedals go, the MXR M133 Micro Amp is one of the best that I've used.  I've used the pedal both for recording and live shows in tandem with a Fender Strat and a '76 Fender Twin Reverb, and find that this is the perfect boost that I need for beefing up my lead tones.  While there isn't much room for versatility, since this is a simple boost pedal I don't mind this all that much.  I find that I'm able to achieve the sound I'm looking for from this pedal with only the gain knob, and it's a sound that I've grown to love.  I often find that I use it for more of a subtle boost than anything else, but it works perfect for me in a lot of situations.


While not everyone needs or wants a booster, the MXR M133 Micro Amp needs to be checked out for anyone who does.  The pedal is very reasonably priced, making it accessible for players on all budgets.  It is perfect for players who want to switch back and forth between lead and rhythm tones quickly for live shows or otherwise.  For anyone who wants a very simple boost pedal that sounds great and won't cost much, the MXR M133 Micro Amp is the way to go.

MGR/beandog's review"MXR Micro Amp"

MXR M133 Micro Amp
Gigging and recording musician for 30 years but got pretty rusty on guitar for a long time (synthesizers took over) but recently inspired by the purchase of a Danelectro 56 Pro, have begun to play again. Currently trying to unlearn all my bad habits but having great fun with a 1974 Fender Vibrolux, Colorsound Wah Wah, Fender Jazzmaster and mxr micro amp.

I got mine in a boot sale for £5 in about 1995. I'm guessing it is a mid-late 70s model, without the red light.

I love the primal simplicity of this box - a rugged chassis, a decent switch, minimal logo and a single enormous black rubber dial (that'll be GAIN, then)....

The bottom is secured rather over-entusiastically by 4 screws and a metal plate, not exactly convenient but a lot better than a flimsy plastic hatch. After about the fourth battery change you'll probably be considering leaving the damn thing off altogether...probably not a good idea though.

The Micro amp does what it says on the tin acts as a pre-amp stage to drive your amp at low levels without altering your tone. You get pure crunch without the fuzzy mess of most distortion units. In my humble opinion most distortion pedals out there are no match for an overdriven valve amplifier. Having said that I quite like a bit of fuzzy mess on the top once in a while :)...Big Muff, anyone?

I would have to say the lack of the light is a bit of a pain. Generally speaking however, when this bad boy is'll know. Other than this little quibble there's nothing to dislike about this pedal.

Basically it's a block of steel. Built like a tank. Go on, kick it around for a while. Then check for broken toes.

The Micro amp is a very simple idea, executed perfectly. When you can't drive your amp too much (neighbours etc.) this will do it for you, without compromising your essential tone. I don't know how it sounds on other amps, but it sounds pretty fantastic with some hot valves!
I haven't been using a distortion unit since my Roger Mayer Mongoose Fuzz got nicked a while back, and am still considering adding a distortion unit, maybe a Rat or a Tube Screamer. But I see the distortion pedal as a kind of final stage for when you can afford to go over the top...then you can back it down to the Micro amp stage and return to your 'real' sound.
I'd just like to say I'm in no way a guitar guru, these are just my personal impressions of gear I own and use. Hope this helps someone.

This review was originally published on

MGR/Jason's review"MXR Micro Amp"

MXR M133 Micro Amp
I purchased my first MXR Micro Amp used on E-bay for about $60. I loved it but it was an older model without a light to let me know when it is on and without an input to allow me to use a wall wart. I bought another one new and paid $90 at a local music store.

I don't know if you can really call this pedal a guitar "effect" because it does not really color my tone in any way. What the Micro Amp does is provide the player with a gain boost. It has one nob that allows you to determine how much of a boost you want. This pedal lets me set my amps volume so that I am where I belong in the mix with the rest of the band and then when i go to play a lead or a subtle finger picking part I can step on the pedal and get that extra juice I need to move out in front slightly. Before i found the MXR Micro-amp i had tried to use an EQ pedal for the same purpose, i found that it was harder to manipulate and actually changed my tone rather than just boosting my signal.

Now that I have the newer model I don't know how I ever lived without the on/off light.

Made very well and it's such a simple concept that there is very little to go wrong.

If you play both rhythm and lead guitar in a project this pedal is great. You won't believe how such a simple function will add to the depth and power of your playing.

This review was originally published on

ManuNZ's review (This content has been automatically translated from French)" Great"

MXR M133 Micro Amp
A switch and a button, nothing more!


Could not be easier I think.


Can boost a clear, or cruncher, or bosster sound. And all this with style! Great sound, warm and dynamic.


I used for quite some years, connected between my head and my Peavey Classic 100 Xotic RC booster. I juggle between the two pedals or I clicks all 2. I have not found better configuration and that for years!
After that, it's all very personal. The pedals never react according to the same amp that is connected behind ... And the guy who plays on it!

ThibautGPP's review (This content has been automatically translated from French)" A killer!"

MXR M133 Micro Amp
RAS, everything has been said. Manufacturing quality and durability beyond reproach.


It could not be simpler because a single knob. The big problem with this pedal is that we want to put it everywhere so it sounds. So I'll take a 2nd to get one in front and one in the chain. Arf


I play with a standard strat and strat rise EMG SA.
The sound is simply HUGE. It has a light color in the top medium that brings so much heat that I have to play in his underwear.

Nothing flashy, not characterized control to the equa amp, shit; there is just a little je ne sais quoi in addition that brings a hell of fishing to your rig. Placed in front, knob at 11am, we really gaining momentum with an intake of discreet but effective gain, and already with a noticeable increase in volume. Really, it's very hard to turn it off once it has begun.

You push the knob in the last quarter and then it starts really cruncher, not to mention the onslaught of decibels that takes in esgourdes.
Note that the sound is slightly cramped. It is still very far from TS like in terms of "nasality."

It goes very well in reinforcement of a more hairy distortion, the micro amp giving the dynamic potential that could break said pedal (it is thanks to him that I did not throw my little big muff, and finally for the moment).

In the loop, the pedal proves just as effective. You lose the contribution of gain to win only on the volume (which is the goal), while keeping the slight coloration makes it really formidable. It transcends the sound on a solo or a riff that we need to attack with more fishing.


I use the micro amp for 2 years and have therefore placed at all possible, parts of my rig.

It's very subjective, but I find it gives the best of itself between 11am and 15:00. In real thing, is connected and gets a big mandala. I would not have imagined that a boost pedal, which is reluctant to buy a little at the beginning to its very appearance "utility" would be such a pillar of my sound.

You'll like her or not, but in any case it really worth trying.
Samuel 6215006/29/2013

Samuel 62150's review (This content has been automatically translated from French)" Simply indispensable!"

MXR M133 Micro Amp
Pedal 100% true analog bypass robust!


A Gain knob, a switch can not be simpler.


I would say it depends on the material used. I use a Vox AC 50 which is already a great amp. The clean Vox is already great but I use this pedal MXR Micro Amp between my guitar and my amp and then the sound is real nice and much more now (I use 40% of the winning race).
Namely, as I'm bassist, I also tested between my bass and my amp (ashdown mag 300) is ideal for bass solos, or even to move from its companion round sound more suited to funky slap.


I use it for 6-8 months now and this is the pedal that I use most in my pedalboard without doubt. The finish is obviously very strong as usual with MXR. Many complain about the location of the power supply but I do not mind it more than that.
The price may be too high for this simple hair gain but well worth finishing, simplicity and the final rendering.
It simply indispensable.
Linn Sondek05/16/2013

Linn Sondek's review (This content has been automatically translated from French)" Any good"

MXR M133 Micro Amp
Pedal preamp, ie boost when the level is raised beyond a certain level. Analog effect as always with MXR. Classical case the brand, robust and compact.


More than easy to use configuration is the simplest it is possible to find an effect pedal.


Here is a boost acting on the volume level. EN according to its position in a chaining, its effect will differ: before or after a distortion, for example, the Micro Amp does not lead in the same way. Before, he played on the level that the attack distortion pedal to increase the gain, according to the same pedal it will just increase the overall volume without changing the gain. From there, so we will try!
The only adjustment available shows progressive and responsive allowing changes both subtle and numerous.
This pedal triggers an addiction quickly and once started it is difficult to pass. We must therefore show great discipline to not abuse it and lose it can do its interest: the effect of "surprise" created its inception.


True to MXR that I know both the range and quality, I have not tried anything else, and took advantage of an opportunity to acquire the Micro Amp. I use it sparingly, avoiding systematize its contribution. For if the effect appears to be relatively transparent, systematic use tends to equalize the sound.
I prefer to use it at the right time and this is what it is: kick boost needed.