The MXR M78 Custom Badass '78 Distortion is a distortion pedal from Dunlop, the first in MXR's Custom Badass series of pedals. It is all analog and true bypass, and it takes a classic distortion circuit, modified by the factory, as the basis for a hot-rodded take on late '70s rock grit12. It sits among MXR's other discrete distortion pedals such as the Dunlop MXR M69 Prime Distortion and the Dunlop MXR FullBore Metal, and more broadly in the world of distortion pedals.
The controls
The M78 keeps things simple: three knobs and one switch.
| Control | What it does |
|---|---|
| Volume | Controls the pedal's output level2 |
| Gain | Sets the amount of grit and distortion2 |
| Tone | Helps pair the pedal with your amp and guitar; adds some sharp top end23 |
| Crunch switch | Boosts the harmonic content2 |
Pedal of the Day's reviewer suggested starting with the gain low and the volume up: "Crank the volume and start with a low gain." At higher gain settings, the reviewer found "grit and hair reminiscent of the late '70s rock acts for which it is named"2.
Where the circuit comes from
MusicRadar's review explains the design approach: "MXR has taken a classic distortion circuit (although it's not saying which!) and modified it to produce a hot-rodded version"3. Pedal of the Day frames the Custom Badass series the same way: "While drawing from a 'classic circuits', the series offers factory-modded pedals to give players new sounds"2. Pedal of the Day's reviewer also found that at low gain it works well with a Telecaster: "You will get a boosted sound that surprisingly goes well with a tele, and I think pairs better than most OCD-type overdr"2.
What reviewers said
MusicRadar's Trevor Curwen summed the pedal up plainly: "this is a really good distortion pedal with plenty to offer"3. Pedal of the Day's David O found a use for it beyond straight distortion, noting that at low gain it works as a boost: "You will get a boosted sound that surprisingly goes well with a tele, and I think pairs better than most OCD-type overdr[ives]"2. His verdict on value: "And to think, you could spend around $70 bucks and get all that"2.
The price has moved since those reviews: Jim Dunlop's product page listed the M78 at $125.99 USD as of October 20261.
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Questions
Is the MXR M78 Custom Badass '78 Distortion true bypass?
Yes. Pedal of the Day's review notes that the M78 is true bypass and all analog, so when the pedal is off your guitar's signal passes through without the distortion circuit loading it down.
Is the MXR M78 an analog pedal?
Yes. The Pedal of the Day review describes it as all analog, with no digital processing in the signal path. It is a straightforward three-knob distortion pedal with an added Crunch switch.
What does the Crunch switch do on the M78?
The Crunch switch boosts the harmonic content, according to Pedal of the Day. In practice it thickens the distortion on top of what the gain knob delivers, giving you a second voicing without turning another knob.
How much does the MXR M78 cost?
Jim Dunlop's product page lists the M78 at $125.99 USD as of October 2026. When Pedal of the Day reviewed it in 2014, the reviewer noted a price of around $70.
What circuits is the Badass '78 Distortion based on?
MusicRadar's review says MXR took a classic distortion circuit, although the company is not saying which, and modified it into a hot-rodded version. Pedal of the Day describes the Custom Badass series as factory-modded pedals drawing from classic circuits.
Sources (3)
- MXR® SUPER BADASS® DISTORTION, Jim Dunlop (www.jimdunlop.com)
- Dunlop MXR M78 Custom Badass '78 Distortion, Pedal of the Day, 2014-07-17
- MXR M78 Custom Badass '78 Distortion review, MusicRadar, 2011-11-11
