Electro-Harmonix Metal Muff

The Electro-Harmonix Metal Muff, sold in its full-size form as the Metal Muff with Top Boost, is an analog distortion pedal aimed squarely at high-gain playing. Electro-Harmonix describes it as "the ultimate metal distortion pedal," with what the maker calls "commanding bass and defined high end-coupled with user-controlled distortion from pinched-edge to totally crushing"¹. Released in 2006, it sits in the Muff family but is built for scooped, heavy tones rather than the classic fuzz of the Big Muff Pi¹².

What sets it apart from most distortion boxes is the EQ section. Three bands, bass, mid and treble, each offer serious cut and boost, and a second footswitch engages a Top Boost circuit that lifts a narrow band of high frequencies so leads stand out over a wall of rhythm guitar¹².

What the Metal Muff does

The Metal Muff is a high-gain distortion pedal in the Muff stable, with a slightly more complex circuit than a regular Big Muff². A 2007 Guitar World review found it could "generate a wide variety of distortion tones-from the deepest, darkest depths of gloom to razor-sharp timbres-capable of shredding ears," crediting its tons of gain, flexible multiband EQ and top-boost circuit³.

The scooped-mids metal sound is handled by the EQ rather than a fixed voicing. Vintage Guitar described the Metal Muff as "set up like an amp, with Treble, Bass, Volume, and Drive controls, plus a useful Scoop toggle and a noise Gate button with accompanying Threshold knob," noting the Scoop offers three choices of midrange attenuation, "great for thrash-metal setups"⁴. MusicRadar's reviewer found the pedal has tighter bottom-end control than a regular Big Muff, suited to angular lead playing, stoner rock riffing and a wall of dirt, and that extreme EQ settings "yield spitting fuzz and marvellous scratchy lo-fidelity voices that are perfect for enlivening a mix or creating dramatic dynamic changes live"².

The controls

The full-size Metal Muff with Top Boost carries Volume, Distortion, and a three-band EQ of bass, mid and treble, plus the Top Boost knob and its own footswitch¹.

The EQ ranges are wide. MusicRadar measured the bass control at 14dB of cut and boost, the mid at 15dB and the treble at 10dB². The Top Boost is active only when its switch is engaged; Guitar World's reviewer called it "great for making solos cut through a dense mix, but unless you're playing an extremely dark-sounding guitar through a dull-sounding amp, you'll probably want to keep the knob rolled down to avoid overly shrill, harsh tones"³.

Power and connections

The pedal runs on the included 9V battery or an optional 9.6VDC-200mA adapter, which is not included; Electro-Harmonix offers the 96DC-200BI supply separately¹. Current draw is 25 mA¹. A mono 1/4" input sits on the pedal's right side, output jacks on its left, and the adapter jack on the top side³. Battery access means removing the four screws that secure the base plate, and MusicRadar expected long battery life despite the more complex circuit².

The enclosure is a tough, compact die-cast chassis¹. MusicRadar described it as sharing the rugged construction of the Little Big Muff "only with a larger case and a pair of footswitches," with amp-style knurled metal knobs and a black and chrome livery².

History and versions

The Metal Muff with Top Boost dates to 2006¹. Since then the design has been scaled down twice.

• Pocket Metal Muff: a smaller edition that, as MusicRadar put it, "lost a lot of big bro's controls," keeping a Master Volume and selectable distortion amount. It was true bypass and shipped with a 9-volt battery. Discontinued in 2020⁵⁶.
• Nano Metal Muff: released in 2021, a "Distortion with Noise Gate" in a chassis about half the size of the original, with six controls: Treble, Mid, Bass, Volume, Gate and Distortion⁷⁸. It keeps the three-band EQ, with treble at +/- 10dB and mid at +/- 15dB of cut or boost, and adds a noise gate "to eliminate feedback and hum"⁹⁵¹⁰. It is buffered bypass, made in the USA, and runs on an included 9V battery or an optional adapter at 24 mA⁷¹¹.

Guitar World's Nano review noted you can get a total of eight different Muffs in Nano-sized enclosures, though only three carry the Nano prefix¹¹. Gearnews described the Nano as delivering "that metal-tinged distortion of the original Metal Muff, but in a much smaller, more pedalboard-friendly form factor"¹², and a Guitar World buying guide said Electro-Harmonix "has taken the concept and shrunk it down, without removing any of the original's penchant for heaviness"¹³.

What reviewers said

MusicRadar's review of the original concluded that "the Metal Muff is a somewhat different proposition that may well appeal to alt rock guitarists and extreme noise terrorists as much as - if not more than - conventional metallers of the old school," and that the Top Boost "really cuts through"². Guitar World's 2007 review praised its gain range and flexible EQ³, while cautioning that the Top Boost can turn shrill on bright rigs³.

Of the Nano, Guitar World's Trevor Curwen listed the three-band EQ as a plus for "plenty control over your sound"¹¹, and Guitar World's launch coverage called its brand of "tonal annihilation" a bargain at its $72 introduction price¹⁴. Delicious Audio's guide to Muff-family pedals highlighted its three-band tone control and noise gate for feedback and hum¹⁰.

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