Every few years, a pedal lands on the market that quietly upends the conversation about what overdrive is supposed to do. The MXR M77 Custom Badass Modified O.D. is exactly that kind of pedal. It looks like a straightforward stompbox — brushed metal housing, four knobs, a small button — but the moment you start twisting those controls, the M77 reveals a depth of tonal flexibility that makes most single-circuit overdrives feel like one-trick ponies.
At its core, the M77 takes a classic asymmetrical clipping overdrive architecture — think Boss SD-1 territory — and upgrades it with two additions that fundamentally change what the circuit can do: a 100Hz cut/boost knob and a Bump switch that reroutes the low-mid EQ voicing. These aren’t cosmetic features tacked on to justify the “Modified” in the name. They turn an already competent overdrive into a precision tone-shaping tool that adapts to your guitar, your amp, and your genre rather than demanding you adapt to it.
Bill Kelliher uses one in Mastodon. Matt Heafy has been documented with it in Trivium’s rig. James Dean Bradfield of Manic Street Preachers runs one in his chain. These aren’t three guitarists chasing the same tone — they’re three players from completely different sonic worlds who all landed on the same box. That alone tells you something worth paying attention to.
The Backstory: MXR’s Custom Badass Family and the 2012 Launch
The M77 made its debut at the 2012 NAMM Show, introduced alongside Dunlop’s Joe Bonamassa signature wah and the Eric Johnson Fuzz Face as part of a wave of MXR releases aimed at expanding the brand’s overdrive lineup beyond its classic stomps. MXR’s Custom Badass series — which also includes the M78 Custom Badass ’78 Distortion — was designed to deliver modern flexibility while staying grounded in the analog signal path that defines MXR’s identity.
The timing was deliberate. By 2012, the overdrive market had fractured into two camps: the low-gain blues-flavored territory dominated by Tube Screamer variants, and the high-gain, amp-tightening territory favored by metal players using pedals like the Boss SD-1 as pre-amp coloring tools. The M77 targeted the gap between these camps and the broader no-man’s-land that most working guitarists actually occupy. With its 100Hz control, the pedal could serve both a Fender-and-single-coil roots rock player who needed more low-end beef, and a Marshall-and-humbucker heavy rock guitarist who needed to carve out laser-precise mids.
Dunlop’s MXR team, working with designer George Tripps — who also contributed to the Way Huge Green Rhino overdrive — built the circuit around asymmetrical clipping in the feedback loop of a 4558-style op-amp. Asymmetrical clipping means the signal is clipped differently on the positive and negative cycles, which generates a different harmonic content from symmetrical clipping (the Tube Screamer family) or hard clipping (most distortion pedals). The result is a slightly more aggressive, less compressed initial character that rewards dynamic playing — dig in harder and the pedal responds with more grit, back off and it cleans up significantly.
Circuit Architecture: Why the 100Hz Knob Is the Real Story
Most overdrives offer three controls: gain, tone, and volume. The M77’s fourth knob — the 100Hz cut/boost — is where the real engineering interest lies. Standard overdrive tone circuits address upper midrange and treble frequencies; the 100Hz control operates specifically at the low-end boundary that separates bass from low-midrange warmth.
Boosting the 100Hz control adds weight and body to the signal — chords become fuller, single notes gain a singing bottom-end resonance, and the overall character gets closer to a wide-spectrum amp overdrive than a midrange-forward pedal overdrive. This is especially useful with Stratocasters into clean Fender amps, where the natural thin-end response of single coils can sound skeletal when driven. Cutting the 100Hz control does the opposite: it tightens the low end, removes excess bass from the signal before it hits an already-saturated amp, and gives lead lines a laser-focused cutting quality that slices through a busy mix without sonic muddiness.
The Bump switch adds another dimension entirely. Engaging it boosts low and mid frequencies together, shifting the overall EQ voicing toward a thicker, more authoritative character that’s particularly effective with humbucker-equipped guitars into medium-gain tube amps. On a Les Paul through a Marshall, hitting the Bump switch transforms the pedal from a versatile boosting tool into something that adds weight and forward presence in a way that recalls an amp being pushed hard by an active cabinet configuration. Premier Guitar’s Charles Saufley, in his 2012 review, described the bump switch plus neck humbucker combination as producing “a throaty, cavernous roar from a 4×12.”
The true bypass switching ensures the M77 exits the signal chain completely when disengaged — no coloring, no tone suck, no buffer interaction. This matters especially for players with longer cable runs who rely on the natural high-frequency roll-off of passive pickups for their clean tone character.
Specs
| Parameter | Specification |
|---|---|
| Model | MXR M77 Custom Badass Modified O.D. |
| Manufacturer | MXR / Dunlop Manufacturing |
| Controls | Gain, Tone, Output, 100Hz (cut/boost) |
| Switch | Bump (low/mid EQ voicing) |
| Bypass | True bypass (hardwire) |
| Current draw | 4mA @ 9V DC |
| Power | 9V battery, Dunlop ECB003 9V adapter, DC Brick, Iso-Brick, or Mini Iso-Brick |
| Circuit type | Asymmetrical clipping analog overdrive |
| Enclosure | Brushed metal, road-ready construction |
| Price (new, 2026) | ~$110–$130 USD (Dunlop list: $125.99) |
| Price (used, excellent, 2026) | ~$60–$90 USD |
| Introduced | NAMM 2012 |
Famous Players: Who Actually Uses the M77
The M77’s player base spans a wider stylistic range than almost any other overdrive at this price point. The confirmed and documented users represent genuinely different musical contexts, which makes the M77 case for versatility concrete rather than theoretical.
Bill Kelliher — Mastodon
The most prominently confirmed M77 user is Bill Kelliher of Mastodon, documented on Dunlop’s official artist roster at jimdunlop.com and cited in the Premier Guitar Mastodon 2014 Rig Rundown. Kelliher — the rhythm guitarist responsible for some of the most technically demanding and sonically complex heavy music of the past two decades — runs the M77 as part of a rig that has evolved to include the Fractal Axe-FX II for modulation and spatial effects. His core guitar-to-overdrive signal path uses Gibson Explorers (including his signature “Golden Axe” Explorer from 2013) through the M77, using the pedal’s 100Hz control to sculpt the low-end response before the signal hits a high-gain amp or the Fractal system.
Kelliher’s use of the M77 in a Mastodon context is significant because Mastodon’s music demands both extreme gain for its heaviest passages and dynamic clarity for the progressive, melodic sections that define albums like Crack the Skye and The Hunter. An overdrive that works in that context has to clean up quickly when gain is reduced, track fast articulate picking without blur, and hold its low-end definition under high-gain amp conditions. The M77 apparently does all of this to Kelliher’s satisfaction. For more on his complete rig, see our Bill Kelliher gear guide.
Matt Heafy — Trivium
Matt Heafy of Trivium is documented on Equipboard as an M77 user. Heafy’s rig has been extensively photographed and catalogued across Trivium’s touring and recording history, and the M77 appears as a drive option in his pedalboard configuration. Like Kelliher, Heafy operates in a genre — melodic death metal / heavy metal — where overdrive is used as both a standalone drive sound and as an amp-boosting tool in front of high-gain head rigs. His guitar arsenal centers on ESP signature instruments, and the M77’s 100Hz control is well suited to the tighter, more aggressive low-end character that downtuned active-pickup guitars running into Mesa or ENGL amplification demand. For more context on Heafy’s complete approach, see our Matthew Heafy gear guide.
James Dean Bradfield — Manic Street Preachers
The M77 appearing in James Dean Bradfield’s rig — as documented on Equipboard — is perhaps the most revealing data point about the pedal’s range. Bradfield is one of British rock’s most distinctive rhythm guitarists: a player whose sound combines Guns N’ Roses-influenced power chord crunch with melodic single-note work, running Gibson Les Pauls and ES-335 style guitars into Marshall amplification. In that context, the M77’s bump switch and 100Hz boost capability serve a completely different purpose than they do for a metal player — here they add warmth and authority to medium-gain rock rhythm playing, thickening chords and preventing the slightly thin, compressed quality that classic overdrive pedals can produce when used with already-warm humbucker/Marshall combinations. The M77 is not in the guitarist DB — prose mention only.
Brendan Bayliss — Umphrey’s McGee
Brendan Bayliss of progressive jam band Umphrey’s McGee is also documented as an M77 user, confirmed in the Umphrey’s McGee 2025 Premier Guitar Rig Rundown as part of his pedalboard alongside a Keeley Compressor, Cusack Screamer, and MXR Timmy. Bayliss’s playing — which covers everything from heavy rock riffing to jazz-influenced improvisation to prog metal — represents yet another musical context where the M77’s flexibility makes it a practical choice. Not in the guitarist DB — prose mention only.
Tone Recipes and Settings
Clean Boost with Low-End Beef (Strat into Fender amp)
Gain: 8–9 o’clock. Tone: noon. Output: 2 o’clock. 100Hz: 2–3 o’clock. Bump: off. This gives single-coil guitars a low-end foundation they don’t naturally have without adding distortion. Good for roots rock, country rock with edge, and Heartbreakers-style rhythm playing.
Classic Rock Crunch (Les Paul into Marshall)
Gain: noon. Tone: 11 o’clock. Output: noon. 100Hz: noon. Bump: on. The bump switch thickens the low-mid response and pushes the overdrive into amp-pushed territory. Works well for rhythm playing in the AC/DC and Stones tradition.
Metal Amp Tightening Boost (Drop-tuned guitar into high-gain amp)
Gain: 8 o’clock (minimum). Tone: noon to 1 o’clock. Output: 2–3 o’clock. 100Hz: 9–10 o’clock (cut). Bump: off. This is the Kelliher/Heafy approach: high output level, minimal gain, cut 100Hz to remove low-end flub before the signal hits a saturated amp. The result is tighter note definition and better pick attack audibility through high-gain distortion.
Lead Guitar Presence Boost (Single-note leads, medium gain)
Gain: 10–11 o’clock. Tone: 1 o’clock. Output: 1–2 o’clock. 100Hz: 9 o’clock (cut). Bump: off. Cutting the 100Hz removes body from the signal and emphasizes upper midrange, giving single-note leads a laser-guided cut that sits above the mix without overwhelming it.
Stoner/Heavy Blues (Humbucker into 4×12, slow riffing)
Gain: 2 o’clock. Tone: 10 o’clock. Output: noon. 100Hz: 3 o’clock (max boost). Bump: on. Both 100Hz and bump together create maximum low-end weight. This is the “shaking buildings” setting that Premier Guitar’s review described — a throaty, cavernous roar that turns slow, heavy riffing into something physically imposing.
Always-On Mild Drive (Stays on all night)
Gain: 8–9 o’clock. Tone: noon. Output: noon to 1 o’clock. 100Hz: noon. Bump: off. Adds barely perceptible grit to a clean signal, bumps the volume slightly for more amp response, and stays out of the way when you want clean clarity. Good as a base layer that other drive pedals stack on top of.
Roots Rock Snarl (Telecaster into 6L6 amp)
Gain: 11 o’clock. Tone: 1–2 o’clock. Output: noon. 100Hz: 2 o’clock. Bump: off. Boosting 100Hz with a Telecaster compensates for the natural bright-and-thin character of single-coil bridge pickups. Gets into Page/Beck Telecaster territory — tough, snarling, with more weight than a clean Tele naturally has.
The M77 rewards methodical dialing-in. Because four controls interact rather than three, the tonal range is wide enough that approaching it without a starting point can feel overwhelming. These settings provide concrete entry points for specific applications.
How the M77 Compares to the Competition
MXR M77 vs. Boss SD-1 Super OverDrive
Both pedals share an asymmetrical clipping architecture using a 4558-style op-amp, which gives them a similar fundamental character — more aggressive and harmonically dense than Tube Screamer-style symmetrical clipping. The SD-1 is a classic at around $50–70 new; the M77 is roughly twice the price. What you gain for that difference is substantial: true bypass versus the SD-1’s buffered bypass, the 100Hz control for low-end shaping, the bump switch for alternate voicing, and a higher-quality build. The SD-1 has decades of track record behind it and delivers a proven sound. The M77 delivers that same basic character plus two major tone-shaping dimensions the SD-1 doesn’t offer. For players who want more than one voice from their overdrive, the M77 is the clearly superior tool.
MXR M77 vs. Way Huge Green Rhino MkIV
The connection here is direct: designer George Tripps worked on both circuits. The Green Rhino is a Tube Screamer-derived circuit (symmetrical clipping, mid-hump character) with a similar 100Hz control. The M77 is asymmetrical clipping, which produces a different harmonic texture — slightly more aggressive, less mid-forward, with better low-end extension when the 100Hz is boosted. Players who love the TS tone and want the 100Hz flexibility should look at the Green Rhino. Players who find TS-style pedals too compressed or mid-heavy — particularly those running humbuckers into Vox or Marshall amplification — may find the M77’s asymmetrical character more to their liking. Both are excellent pedals at similar price points; the choice comes down to clipping topology preference.
MXR M77 vs. MXR M78 Custom Badass ’78 Distortion
The M78 is the M77’s sibling in Dunlop’s Custom Badass line, designed to evoke the hard-edged distortion character of 1978-era Marshall-driven rock — more gain, harder clipping, more aggressive saturation. Dunlop’s own description recommends running the M77 in front of the M78 for “a slew of amp-like gain structures that won’t mask your tone.” This pairing — M77 as low-gain drive shaping the frequency content, M78 as high-gain distortion character — represents a sophisticated dual-pedal approach that can cover everything from medium crunch to full-on hard rock distortion while maintaining clarity and note definition throughout the gain range.
MXR M77 vs. MXR M249 Super Badass Dynamic O.D.
The M249 is MXR’s more recent evolution of the flexible overdrive concept, with a 3-band EQ (treble, mid, bass) instead of the M77’s simpler tone/100Hz layout. The M249 offers more surgical EQ control; the M77 offers a simpler but still highly effective approach with the addition of the bump switch voicing. Players who want maximum parametric control over every frequency band may prefer the M249. Players who want a fast, intuitive adjustment system — one knob for low-end character, one for overall tone — often find the M77’s approach more usable in live performance contexts where there’s no time for complex dialing.
MXR M77 vs. Ibanez TS9 Tube Screamer
These are genuinely different pedals. The TS9 uses symmetrical clipping (both cycles clipped equally) and a fixed mid-hump that’s part of its identity — that bump is both its greatest asset (cut-through, blues vocal quality) and its greatest limitation (if you don’t want the mid-hump, you can’t remove it). The M77’s asymmetrical circuit has no inherent mid-hump; the bump switch adds midrange if you want it. For players who’ve always found Tube Screamers too compressed or too mid-forward with humbuckers, the M77 offers a fundamentally different overdrive flavor at a similar price. For players who specifically love the TS tone, the TS9 is the right tool.
Buying Guide: When the M77 Is the Right Call
The M77 makes the most sense in three specific situations. First: you play multiple genres in the same set or the same gig — country rock one night, heavier stuff the next — and need one overdrive that can honestly serve both without sounding like a compromise in either direction. The 100Hz control lets you dial the low-end character to match whatever amp and guitar combination you’re running. Second: you’re running a high-gain amp and want a boost/OD in front that tightens the low end rather than adding to it. The 100Hz cut is precisely the tool for this, and the M77 delivers it within an overdrive that has more character than a purely transparent boost. Third: you’ve tried Tube Screamer variants and found them too compressed, too mid-heavy, or too limited in tonal flexibility. The M77’s asymmetrical circuit and broader EQ range may solve the issues you’ve been encountering.
Where the M77 is not the obvious choice: if you specifically want the classic TS “voice” that cuts through a band mix with midrange push and warm compression, you’ll get there faster with the TS9 or TS808. The M77 is not a Tube Screamer variant and doesn’t have that voicing. And if budget is the primary constraint, the Boss SD-1 delivers a comparable asymmetrical clipping character at roughly half the price — though without the 100Hz control and bump switch.
Current street prices for the M77 sit around $110–$130 new from authorized retailers, with used examples in excellent condition typically landing at $60–$90. It’s not an expensive pedal by boutique standards, and the build quality — brushed metal housing, solid footswitch, MXR’s road-tested construction standards — means a used unit bought in good condition should perform identically to a new one. This is a pedal to buy for the long haul.
Ownership Notes
The 4mA current draw is exceptionally low — about as low as any modern overdrive pedal, and lower than most digital effects by a factor of ten or more. Any 100mA isolated output on any standard pedalboard power supply handles the M77 effortlessly. Power budget planning is essentially irrelevant with this pedal.
The bump switch is fixed in position — it cannot be engaged or disengaged with your foot during performance without reaching down to the side of the pedal. Premier Guitar’s review noted this as a limitation: if you want the bump voicing on some songs and off on others, you’d need to add a second M77 to the board or plan to make the switch change during a break. For most players, picking either bump-on or bump-off as a default setting and leaving it there makes practical sense.
The 100Hz control interacts most noticeably with the gain setting. At very low gain levels, cutting 100Hz produces a thin, slightly hollow character that’s rarely useful. At medium to high gain settings, the 100Hz cut becomes highly effective — tighter, more focused, with better pick-attack definition. It’s worth spending time with the gain and 100Hz controls together rather than treating them as independent adjustments.
Stacking the M77 in front of another drive works very well in both directions. Running it first in a drive chain — M77 into a higher-gain pedal — lets the 100Hz control shape the frequency content going into the next stage, which affects how the subsequent pedal saturates. Running a lighter drive (like a mild overdrive or compressor) into the M77 layers gain structures in a way that can produce complex, harmonically rich drive tones without the fizz or blur that stacking two high-gain pedals typically creates.
FAQ
Is the MXR M77 a Tube Screamer clone?
No. The M77 uses an asymmetrical clipping circuit, not the symmetrical clipping architecture that defines the Tube Screamer family. The fundamental harmonic character is different — less compressed, less mid-forward, with more low-end extension when the 100Hz is boosted. It’s closer in character to the Boss SD-1 than to the TS9, though both the 100Hz control and bump switch give it tonal flexibility that neither the SD-1 nor any stock TS9 offers.
What’s the bump switch actually doing to the signal?
The bump switch engages an alternate EQ voicing that simultaneously boosts low and midrange frequencies. It shifts the character of the pedal toward a thicker, more forward sound — useful for heavy rhythm playing, adds authority to blues leads, and works particularly well with neck humbuckers into medium-gain tube amps. It cannot be engaged with your foot during performance.
Can the M77 work as a metal drive?
Yes, in two distinct ways. As a standalone overdrive with the gain cranked, the 100Hz and bump controls can dial in genuinely aggressive tones, though it’s not a high-gain distortion pedal — it doesn’t do metal on its own. More effectively, it serves as a tight, low-gain boost in front of a high-gain amp (like a 5150, Mesa Rectifier, or ENGL), using the 100Hz cut to remove low-end flub before the signal hits the amp’s preamp stage. This is exactly how Bill Kelliher uses it with Mastodon.
Does the M77 have a battery option?
Yes, the M77 can be powered by a standard 9V battery in addition to Dunlop’s ECB003 adapter and compatible power supplies (DC Brick, Iso-Brick, Mini Iso-Brick). With a 4mA current draw, battery life is reasonable for practice use, though for consistent gigging a dedicated power supply output is the more reliable option.
How does the 100Hz control change when stacked with another drive?
When the M77 runs first in a drive stack, the 100Hz setting shapes the EQ content going into the next pedal. Boosting 100Hz sends a warmer, fuller signal into the subsequent stage; cutting it sends a tighter, more focused signal. This affects how the next pedal saturates — a 100Hz-boosted M77 into a Tube Screamer creates a thick, warm overdrive stack, while a 100Hz-cut M77 into the same TS creates a more aggressive, defined sound. Experimenting with the 100Hz position while the stack is active rather than in isolation gives the most musically useful results.
Is the M77 the same circuit as the Way Huge Green Rhino?
Not exactly, but they share a design heritage — both were developed with input from George Tripps. The Green Rhino is Tube Screamer-derived (symmetrical clipping, inherent mid-hump) with a similar 100Hz control. The M77 uses asymmetrical clipping (no inherent mid-hump), which is why the two pedals sound different despite their shared DNA. The bump switch on the M77 adds midrange, but it’s a different voicing than the Green Rhino’s inherent symmetrical-clipping mid character.
What’s the best amp pairing for the M77?
The M77 is amp-agnostic by design — the 100Hz control lets it match its low-end character to whatever amplifier it’s running into. With Fender-style clean amps and single coils, boosting 100Hz adds weight the amp and pickups naturally lack. With Marshall-style mid-heavy amps and humbuckers, cutting 100Hz removes excess bass and tightens the response. With high-gain amps, minimum gain and maximum output is the standard approach. The M77’s flexibility specifically means there’s no “wrong” amp pairing — there’s only a 100Hz setting that may need adjustment for each new rig.
How does the M77 compare in value to boutique overdrives?
At $110–$130 new, the M77 sits significantly below the boutique market ($150–$350+) while offering two control dimensions — the 100Hz knob and bump switch — that many boutique pedals at twice the price don’t provide. The MXR build quality is genuinely road-worthy; there are M77s that have been touring for over a decade without hardware failures. For players evaluating boutique versus mass-market options, the M77 represents a case where the mass-market option delivers performance features the boutique sector often lacks at the price point.