The Electro-Harmonix Metal Muff with Top Boost is an analog distortion pedal released by Electro-Harmonix in 20061. It is the high-gain member of the company's Muff line: Electro-Harmonix describes it as delivering "commanding bass and defined high end-coupled with user-controlled distortion from pinched-edge to totally crushing"1. Where a classic Big Muff leans toward fuzz, the Metal Muff is built for heavy, amp-like gain with a full EQ section and a footswitchable treble boost for solos.
MusicRadar called it "the newest addition to the Muff stable" at its release, and Guitar World's 2007 review noted that its "tons of gain, flexible multiband EQ and a top-boost circuit" let it "generate a wide variety of distortion"23.
What the Metal Muff does
The pedal is aimed squarely at high-gain, metal-style tones. The three EQ bands are the heart of it: Electro-Harmonix says the Metal Muff "utilizes three powerful EQ bands" that let a player shape the midrange, which is where most metal tones live or get cut1. MusicRadar's review measured the mid control at 15dB of cut and boost, and the maker rates the treble control at up to 10dB of cut and boost21.
The Top Boost is the pedal's signature feature. Electro-Harmonix says it "provides an extra 'bite' by boosting a narrow band of high frequencies"1. MusicRadar explained the intent: Electro-Harmonix included the feature "with a view to ensuring that those riffs and solos scythe through a dense mesh" of dirty rhythm guitar2.
"When engaging the Top Boost, be careful of the amount of extra bite it can deliver as things can get pretty searing."
The controls
The front panel is laid out like an amp, with knobs for tone and gain plus two footswitches. Vintage Guitar's 2014 review of the Tone Tattoo multi-pedal, which included a Metal Muff section, described it as "set up a like an amp, with Treble, Bass, Volume, and Drive controls"4.
| Control | What it does |
|---|---|
| Distortion knob | Adjusts the amount of input gain1 |
| Volume control | Sets the output level1 |
| Treble knob | Up to 10dB of cut and boost in the treble range1 |
| Bass and mid knobs | Complete the three-band EQ1 |
| Top Boost control | Boosts a narrow band of high frequencies for extra bite1 |
| Bypass footswitch | Engages or bypasses the effect; LED lights when engaged1 |
| Top Boost footswitch | Engages the Top Boost; its own LED lights when on1 |
Guitar World's 2007 review described the hardware as "two heavy-duty footswitches at the lower right and left corners" that "engage bypass and top boost functions, respectively," with "blood-red LED indicators"3. The review also noted a practical detail: the top boost function "is active only when the boost switch is engaged," so the boost knob's setting only matters once the second footswitch is on3. The same review noted that "a jack for an optional nine-volt adapter is situated on the top side" of the chassis3.
Power and connections
The Metal Muff runs on a 9V battery, which is included, or on an optional 9.6VDC 200mA power adapter, which is not1. Current draw is 25mA, modest by modern standards, so a battery is a realistic option for players who do not want to add a power supply1. The optional adapter is Electro-Harmonix's 96DC-200BI supply1.
Connection is simple: one 1/4" input jack and one 1/4" output jack1. The bypass is buffered rather than true bypass, with a high input impedance buffer that preserves the guitar signal when the pedal is off1. The pedal sits in what the maker calls a "tough and compact die-cast chassis" at 5.75 x 4.75 x 2.5 inches1.
History and versions
The Metal Muff with Top Boost dates to 20061. It has since been scaled down twice.
- Nano Metal Muff (2021): a compact version that keeps the high-gain character and a full tonestack EQ, with Volume, Distortion, Treble, Mid and Bass controls plus a Gate knob, according to Guitar World's review56. It is analog, uses buffered bypass, and runs on a 9V battery with the same optional 9.6VDC adapter5. It lists at $84.40 USD5. GuitarPlayer noted that "the pedal lacks the original's footswitchable Top Boost"7, and MusicRadar observed that when Electro-Harmonix "scaled it down before for the Nano range for the 'Pocket' edition, it lost a lot of big bro's controls," the Nano brings more of them back8.
- Pocket Metal Muff (discontinued 2020): the smallest version, with a Master Volume control, selectable distortion amount, true bypass, and a 9V battery9. Electro-Harmonix discontinued it in 20209.
| Version | Status | List price | Bypass | Notes |
|---|---|---|---|---|
| Metal Muff with Top Boost | Current | $108.90 USD1 | Buffered1 | Footswitchable Top Boost78 |
| Nano Metal Muff | Current | $84.40 USD5 | Buffered5 | No Top Boost footswitch7 |
| Pocket Metal Muff | Discontinued 20209 | True bypass9 | Master Volume only9 |
What reviewers said
Guitar World's 2007 review found the pedal versatile, praising its gain range and EQ flexibility, and highlighting the top boost as "great for making solos cut through"3. MusicRadar's review echoed that, with the caveat about the Top Boost's intensity noted above2.
The Nano version has drawn its own press. Guitar World's buying guide of cheap distortion pedals named it the "Best cheap distortion for metal," writing that Electro-Harmonix "has taken the concept and shrunk it down, without removing any of the original's penchant for heaviness"10. Guitar World's full review of the Nano lists it as a "Fuzz/distortion pedal" at $84 / £796.
Videos
EHX
THE MUSICIAN NETWORK (TMNtv)
ช่างหาทำ
Questions
Is the Metal Muff with Top Boost true bypass?
No. Electro-Harmonix lists the Metal Muff with Top Boost as buffered bypass, with a high input impedance buffer that keeps the pedal from loading down the guitar signal when it is off. The smaller Pocket Metal Muff was true bypass, but the full-size and Nano versions use buffered bypass.
Does the Metal Muff come with a power supply?
A 9V battery is included in the box, but the power adapter is not. Electro-Harmonix offers an optional 9.6VDC 200mA adapter, sold separately, and the pedal draws 25mA, so a battery lasts a good while at occasional use.
What does the Top Boost footswitch on the Metal Muff do?
It engages a boost that pushes a narrow band of high frequencies for extra bite, with its own LED to show when it is on. Reviewers found it useful for making solos cut through dense rhythm guitar, though MusicRadar warned it can get pretty searing at high settings.
What is the difference between the Metal Muff and the Nano Metal Muff?
The Nano Metal Muff, released in 2021, is a compact version of the same high-gain distortion idea with a full tonestack EQ, but it drops the original's footswitchable Top Boost. The full-size pedal also adds a dedicated Top Boost footswitch and LED. The Nano lists at $84.40 against the original's $108.90.
Is the Metal Muff a fuzz or a distortion pedal?
Electro-Harmonix classifies the Metal Muff with Top Boost as a distortion pedal, and it sits in the Muff family of circuits. It delivers high gain with a three-band EQ, aimed at heavy and metal tones rather than the softer clipping of a classic fuzz.
How much does the Electro-Harmonix Metal Muff cost?
The Metal Muff with Top Boost lists at $108.90 USD on Electro-Harmonix's product page as of October 2026. The Nano Metal Muff lists at $84.40 USD, and Guitar World's review of the Nano gave its price as $84 with a UK price of £79.
Sources (10)
- Metal Muff with Top Boost, Electro-Harmonix (ehx.com)
- Electro-Harmonix Metal Muff review, MusicRadar, 2008-01-03
- Electro-Harmonix Metal Muff, Guitar World, 2007-04-26
- Electro-Harmonix Epitome, Tone Tattoo, Vintage Guitar magazine, 2014-12-16
- Nano Metal Muff, Electro-Harmonix (www.ehx.com)
- Electro-Harmonix Nano Metal Muff review, Guitar World, 2023-11-01
- Electro-Harmonix Unveils New Nano Metal Muff Distortion Pedal, GuitarPlayer, 2021-01-04
- Electro-Harmonix scales down with the new Metal Muff Nano, MusicRadar, 2021-01-04
- Pocket Metal Muff, Electro-Harmonix (ehx.com), 2020
- Best cheap distortion pedals: get your perfect rock tone for less money, Guitar World, 2024-01-31
