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MXR M85 Bass Distortion Review

This collaboration with Fuzzrocious delivers heavy loads of bass distortion.

MXR’s M85 Bass Distortion was born out of a desire to create something a bit more extreme than the company has previously produced. To make this happen, the MXR crew reached out to Fuzzrocious Pedals founder Ryan Ratajski and proposed a collaboration to craft the ultimate modern bass-distortion pedal. This meeting of the minds resulted in the M85—a stomp that howls with a bold ferocity and packs a level of intensity that reaches far beyond most other off-the-shelf pedals in its class.

The Right Stuff
Operating the M85 couldn’t be simpler. Its 9V-powered analog circuit uses LED and silicon diode-based clipping, either of which can be selected via an illuminated push-button on the pedal’s face. The silicon-diode mode is the most compressed sounding of the two, while the LED mode has a wider tone with more volume and a slight gain boost.

There are controls for tone and distortion levels, as well as dedicated dual volumes for the dry and wet signals. Here’s what’s particularly nice about the dry and wet dials: When they’re set to noon, they’re exactly at unity volume with one another. This uniformity in their tapers makes it very easy to dial in the perfect blend of unaffected and wet signals without losing definition and bite.


Dual clipping modes offer a wide range of ballsy bass distortion. Separate wet and dry dials allow for exceptional definition. Solid, affordable, and simple to use.

The higher-gain tones are not for the meek.


Ease of Use:




MXR M85 Bass Distortion

Collapse and Crush
To test the M85’s mettle, I enlisted a rig consisting of a Fender P and an Ampeg SVT reissue with a matching 8x10 cabinet. In silicon-diode mode, the pedal delivered a fantastic bass grind with its dry and wet levels set to noon, and the tone and distortion knobs at 11 o’clock. Rolling back the Precision’s volume control reined in the gain’s intensity nicely.

Fans of the RAT-like Fuzzrocious Rat Tail distortion pedal (recently renamed the Cat Tail) will feel right at home with the M85. With a Homer Simpson-like level of gain gluttony, this is a pedal for serious distortion addicts. The M85 lent itself to everything from long-sustaining notes and fast-legato runs to thick, pummeling chords on my P’s lower registers. And with careful tuning of the wet and dry volumes, the low end remained tight and focused without degrading into mush. The distortion had a raw edginess to it that couldn’t be completely dialed out using the pedal’s tone knob, but setting it between 8 and 10 o’clock along with a higher dry volume yielded smoother sounds that worked well for classic Jaco-inspired grit.

Compared to the silicon-diode mode, LED-mode tones possess a bigger midrange and sound wider. I found there was also a serious boost in the attack, which was faster and ballsier than before. This makes the LED mode more useful for vintage classic-rock tones with low-gain settings. After cranking the distortion to 5 o’clock and the wet knob to 2 o’clock, the M85 unleashed one of the more fierce and powerful bass-distortion tones I’ve come across in a long time—akin to a love child born from Lemmy’s tone and the hellhound growl of Italian doom masters Ufomammut.

The Verdict
Cash-conscious bassists who’ve been clamoring for an affordable high-gain stompbox with boutique tone don’t have to look much farther than the M85 Bass Distortion. Its raw and fluid distortion, crushing power, and supreme clarity make it an ideal choice for raw, blue-collar metal tones à la High on Fire and Converge. Its two distinctly different clipping modes and separate dials for the wet and dry signals give it a diverse palette of grinding tones. While the M85’s best sounds often come with modern, bristling edges, the pedal can cover classic rock and metal overdrive with ease, provided the distortion and volume controls are used conservatively.

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