MXR M81 Bass Preamp

Bass Preamp Pedal with XLR Direct Out, 3-band EQ, and Level Controls
MXR M81 Bass Preamp image 1
MXR M81 Bass Preamp image 1
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MXR M81 Bass Preamp
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MXR Bass Innovations Preamp Pedal

For studio-quality bass tones wherever you play, rely on the MXR M81 Bass preamp pedal. Separate input and output level controls let you take advantage of MXR's innovative Constant Headroom Technology for clarity at volumes other preamps just can't produce. The flawless direct out can be sent to the house pre or post the 3-band, sweepable midrange EQ section - dial in tone for your amp and leave the PA to the sound chick. To get a new tone from an old bass or amp, or for just a touch of something every now and then, the versatility of the MXR M81 Bass preamp pedal is what you need.

Dunlop legacy and MXR

Dunlop Manufacturing started in 1965 much like Sweetwater, a family-owned and operated company. In 1972 Dunlop introduced the MXR pedals and quickly established themselves as pioneers in the guitar effects pedal market. Their continuing innovations are highly-acclaimed, winning multiple awards with their Bass Innovations line and presenting the guitar-playing world with new classics like the Carbon Copy delay pedal. The MXR Custom Shop delivers you the classic MXR pedals made from original specs and gives you a touch of 'boutique' with special runs of guitar effects pedals. Sweetwater is proud to partner with Dunlop to give you the best MXR has to offer!

MXR M81 Bass Preamp Pedal Features:
  • Switchable pre/post EQ direct out - get the right tone for your amp and the room
  • High headroom input and output level controls for distortion-free signal
  • 3-band EQ section with sweepable midrange dials in whatever you need
  • Buffered bypass/True bypass switchable for even greater versatility
  • Operates on 9V battery, optional power supply, pedalboard power, or phantom power from your mixer
Put award-winning tone at your feet with MXR Bass Innovations pedals!

Tech Specs

Type Bass Preamp
Form Factor Pedal
Inputs 1 x 1/4"
Outputs 1 x 1/4", 1 x XLR (DI out)
True Bypass Switchable
Power Source 9V DC power supply (sold separately)
Batteries 1 x 9V
Weight 1.5 lbs.
Manufacturer Part Number M81

Customer Reviews

Based on 8 reviews
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Nice little preamp

Great preamp in a small package. I use this on my pedal board mainly to control tone,and not as a DI, so I can't comment on that. It's clean, quiet, and provides a wide variety of tones. I like to scoop the mids a bit, and this does that by simply setting both the bass & treble at 3;00 and leaving the mids flat or slightly boosted at 800K. It's a little pricey, but it gives me the sound I want and seems to be well made,
Music background: Semi-pro for 40 years

an added tonality

this bass preamp gives a get selection of tonality to make any bass you play sound their best.
Music background: semi-pro

A great-sounding stomp box!

What a great sounding pre-amp/E.Q. this thing is! The mid-range control, being semi-parametric, is great for finding that sweet spot in your tone, be it boost OR cut (in my case, a -7-10db cut around 600hz). The bass and treble controls a shelving types, so they offer quite a warmth and sparkle to your tone as well. Do they add thunder or snap? Not really in my application, which is as a "real" pre-amp, but they are quite usable and offer a very wide range of boost or cut. As I've said, I'm using the M81 as a true pre-amp; that is to EQ the instrument and get the gain up enough to drive a power amp, rather than just change tones around and then plug into an amp- First, it is one of the two real EQ sections I have in my rig (the second being an EMG EXB ("smiley face EQ) built into a stomp box case and selectable rather than hacking apart my instrument. the other "real" pre-amp duty this thing offers is output level. It is great for D.I.'ing into the board (for either recording or live). Output level is quite amazing- I use it to drive my power amp (and SWR Stereo-800) which in turn drives an Ampeg SVT810E speaker. I have run the input and output controls full up, and this thing doesn't clip! The idea of MXR's "constant headroom technology" is something that adds a great amount of value to this pedal. Get one!!!


This is a fabulous pedal. It holds a very wide range of tone shaping capability, and it does very little to color your bass' tone. The mid sweep is a wonderful feature, and the separate input/output levels really help dial in the right sound. I even use the M81 as a sort of boost pedal when I'm playing through my M89 overdrive; the it really brings out the crunch when I raise the mids and/or treble. I play an active Ibanez.
Music background: performer, composer, hobbyist, almost 15 years music experience

MXR M81 Bass Preamp

I received this in early June and have already used it on three gigs with my Fender P-bass (passive). I've been searching for a small pedal preamp that I can mount on my pedal board. Most of the ones out in the market and large in size. The other larger ones I own are great but they're too large in size for my pedal board. I really like how the EQ on this pedal is voiced, and its very quiet. Don't hesitate. Get one. You will not be disappointed. MXR, you hit one out of the park with this one. Bravo!
Music background: Pro bassist

Sweetwater Advice

MXR Bass Preamp

A significant boost with the input dial and a slight bump with the bass control began an instant tone resurrection. Whether you're looking to give your vintage bass a modern vibe without having to route the body, or you seek a solo-boost or tonal-tweaking device to cut through the mix, or you need a solid DI that will work well for both the stage and studio, you're pretty much covered with the MXR M81....
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See also: Bass Effects, MXR, MXR Bass Guitar Pedals & Effects