There’s a meaningful difference between overdrive and distortion on bass, and it’s worth being clear about it before diving into the M85. Overdrive adds harmonic saturation while preserving most of the original signal character — it’s a gentle to moderate effect. Distortion replaces much of the original signal with clipped, harmonically rich output. The difference in practice is the difference between “warm and gritty” and “aggressive and transformed.”
The MXR Bass Distortion M85 is firmly in distortion territory. It’s not trying to sound like a cranked amp. It’s trying to sound like a distortion pedal — and it does that job well.
Controls and Architecture
The M85 has four controls: Distortion, Tone, Dry, and Wet. That Dry/Wet split is the key feature that separates this from a standard distortion pedal. The Dry control sets the level of your clean bass signal. The Wet control sets the level of the distorted signal. You blend them independently.
This matters enormously for bass. A common problem with distortion on bass is losing the low end — the clipping process that creates distortion doesn’t handle low frequencies as cleanly as mids and highs. If you run 100% distorted signal you often end up with something that sounds aggressive in the upper range but has no foundation underneath. The Dry/Wet blend lets you keep your clean low end while adding distortion to the mids and highs. The result is full-range bass with aggression on top.
True bypass switching, 9V standard operation, MXR’s usual robust aluminium enclosure. The build is solid and road-worthy.
Tone Character — What It Actually Sounds Like
The M85’s distortion circuit has a tight, focused character. It’s not a fuzz — there’s no loose, woolly quality. The distortion is controlled and articulate even at high gain settings. Notes remain somewhat distinguishable through the effect, which is important for bass where melodic clarity matters even under dirt.
At moderate Distortion settings with the Dry around 50% and Wet at 70-80%, the M85 produces an aggressive rock bass tone that sits extremely well in a guitar-heavy mix. The clean dry signal holds down the low end, the distorted wet signal cuts through the guitars. You’re present and defined without fighting for space.
Push the Distortion higher and the character gets more extreme — closer to metal territory. Still controlled, still articulate, but unmistakably aggressive. The Tone knob pulls the frequency emphasis around without being a full EQ — think of it as a presence control that adjusts where in the midrange the distortion character lives.
At full Wet with no Dry signal you get pure distortion — this is where it sounds most like a guitar through a distortion pedal and least like a bass. Useful for specific sounds but not where the M85 is most musically functional for bass playing.
Comparing M85 to M89 Overdrive
I reviewed the MXR Bass Overdrive M89 recently and the comparison is worth making directly. These are different tools for different situations.
The M89 is warm, medium-gain, with a controlled character that works for rock, soul, and R&B where you want grit without transformation. It’s a “make it more interesting” pedal.
The M85 is aggressive, high-gain, with a character that actively transforms the bass tone. It’s a “change what this sounds like” pedal. If you play music where distorted bass is a feature rather than a subtle addition — hard rock, metal, stoner rock, noise rock — the M85 is the right choice.
If you want one MXR dirt pedal for general use, the M89 is more versatile. If you specifically need distortion rather than overdrive, the M85 does it better.
The Dry/Wet Blend in Practice
I want to emphasise this feature again because it’s what makes the M85 genuinely useful rather than just another distortion pedal. I’ve run sessions where I had the Dry at full and gradually brought in the Wet during a take — starting clean and introducing distortion without losing the low-end foundation. That kind of control makes a real difference in recording situations.
Live, the blend gives you the ability to fine-tune how aggressive you sound relative to the mix. If the guitars are already dense you back off the Wet. If there’s space you push it up. It’s a more musical approach to distortion than a simple on/off effect.
Who Should Buy the MXR Bass Distortion M85
Rock and metal bassists who need distortion that preserves low-end definition. Players who want the flexibility of independent clean/dirty blending. Anyone who’s been frustrated by standard distortion pedals losing the bass frequencies.
Not ideal for players who want subtle overdrive — the M89 or similar medium-gain pedal is the better choice there. Not ideal for jazz, soul, or styles where distortion has no place. The M85 is a specialist tool and it does its specialty extremely well.
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FAQ
What is the difference between the MXR M85 and M89?
The M89 is an overdrive — warm, medium-gain, adds grit without transforming the signal fundamentally. The M85 is a distortion — aggressive, high-gain, actively transforms the tone. The M85 also has an independent Dry/Wet blend that the M89 doesn’t. For subtle grit use the M89; for aggressive distortion use the M85.
Does the MXR M85 preserve low end?
Better than most distortion pedals, specifically because of the Dry/Wet blend. By keeping the Dry signal at a useful level you maintain clean low-end foundation while the distorted Wet signal adds aggression in the mids and highs. Run 100% Wet with no Dry and you’ll lose low-end definition like any distortion pedal.
Can I use the MXR M85 with active pickups?
Yes. Hot active pickups will drive the Distortion control harder so you may need to set it lower than with passive pickups to achieve the same gain level. The pedal handles high-output signals without issue.
Is the MXR M85 good for metal bass tone?
Yes — the tight, articulate distortion character works well for metal. Keep the Dry blended in to maintain low-end punch, push the Distortion high, set the Tone to taste. It’s not as extreme as dedicated metal distortion pedals but it covers hard rock through modern metal territory effectively.
Does the MXR M85 have true bypass?
Yes. True bypass means the pedal is completely out of your signal path when switched off — no tone colouration, no signal loss. Standard 9V centre-negative power supply, compatible with all major pedal power systems.