'The MXR Bass Preamp combines a pristine bass preamp with a studio-quality Direct Out in a Phase 90-sized box, providing clear tone without hogging precious pedalboard space. Use it to add a new voice to an old passive bass, sweeten up any amp, or put some special sauce on a particular song. Dial it in just the way you want it and send it straight to the house — pre or post-EQ — with the built-in Direct Out.
'The MXR Bass Preamp features separate INPUT and OUTPUT level controls and a 3-band EQ section with sweepable midrange — from 250hz to 1khz — for extensive tonal flexibility. It's all delivered super-clean with high headroom thanks to our own Constant Headroom Technology™, and you can use the PRE/POST EQ switch to set whether or not your Direct Out signal is affected by the Bass Preamp's EQ section. And the Bass Preamp features a GROUND LIFT switch in case you encounter ground loop hum.
'The MXR Bass Preamp is pre-set to operate in 1/4" Out buffered bypass and Direct Out active. For players who only want to use the 1/4" Out, there are two internal switches that disable the Direct Out and 1/4" Out buffered bypass for true 1/4" Out bypass mode.'
Now read on:
I have bought, used and sold many onboard and outboard bass preamps of various flavours over the years - VT Bass, Behringer BDI-21, Markbass Super Booster, Zoom B3, B1on, B1Xon and MS-60B, MXR M80, DHA VT1, Tone Hammer, Audere JZ3, East P-Retro, EMG BTS, Spector TonePump, TonePump Jr, most of the various types of Guitar and bass Sansamps... and so on and so forth.
I suppose the nearest thing to the M81 I've used would be the MXR M80. I liked the M80 a lot for its big clean-channel tones, but not so much for it's distortion facilities, so reluctantly I moved it on.
However, the difference between the M81 and much of the competition at this price point is the 3-band EQ with sweepable mid control. I've no idea what the 'Q' is set to, but it can't be too wide as blithely cutting or boosting the mids does not overly interfere with your bass or treble settings. This is a good thing.
The input and output controls can provide lots of clean boost and together they are very user-friendly. Unity gain on a board would be a doddle. There is nothing that is not useful and there are no superfluous bells or whistles. The build quality is as you would expect from Dunlop/MXR and the action of the controls feels very positive.
The M81 is also fairly unique in that it provides no crunch, grind, grit, hair, fuzz, growl or distortion of any kind and doesn't radically change your tone in an obvious way - it's very transparent in use and very clean and quiet in operation - yet it imparts a vivid, crystal-clear warmth.
So if you're already happy with the core tone of your bass (as I am - Fender Road Worn P with La Bella flats) then the M81 will keep it intact but also render it sonically epic, somehow. Plus you can add more punch in the mids, iron out any frequency lumps and bumps that a crap-sounding room may introduce, bring forth a full, tightly-controlled bottom (fnarr) and dial in an airy (but not strident) top end. Which is nice.
I have a Markbass SA450 - itself an amp that sounds great just as it is - but the M81 really brings it to life, turning an already very capable and articulate amp into a muscular Balrog of Warm Clean Heft. I suspect this would be a perfect preamp to drive a power amp. It would also be interesting to try it on the front of an all-valve power amp for that big-bounce slam.
In short it's a powerful, flexible and very useful little box with a cracking circuit in it that gives your sound great clarity and warmth, apparently without artifice, which is a neat trick. How much of this is down to MXR's proprietary Constant Headroom Technology™ is something of a mystery, as even via the gift of Google I've so far been unable to find out exactly what it is. Marketing, probably.
No matter, the M81 is a great-sounding pre/DI and it's easy to imagine it being used as an always-on device both live and in the studio. It's also something of a bargain... at least compared with some of its peers. Buy used for around the £100-mark - if you can find one. Recommended.
Edited by discreet, 03 January 2017 - 11:23 PM.