Mojo Hand FX Iron Bell

The Mojo Hand FX Iron Bell is a fuzz pedal built around the Big Muff circuit family, but it is not a copy of any one vintage Muff. Mojo Hand FX describes it as a "Gilmour" fuzz, and says the circuit "isn't based on any particular Muff circuit. Instead, we've tweaked it to be a platform that is wide, yet focused"¹. The maker voices it "to be very open and rich, with an almost 3D-like harmonic quality"¹, a description the tagboardeffects circuit analysis repeated when it covered the pedal in 2013².

Within the Mojo Hand FX lineup, the Iron Bell sits apart from the Colossus, which the maker bases on the Russian/Civil War era Muff¹. Where the Colossus chases a specific era of Muff, the Iron Bell is its own take on the format.

A Big Muff-style fuzz with an open voicing

The tagboardeffects analysis put the circuit in plain terms: "all this circuit is, is a big muff with a mids control"². That mids control is the main thing separating the Iron Bell from a stock Big Muff, where the tone stack famously scoops the midrange. Coda Effects, in its Big Muff tone stack analysis, groups the Iron Bell with the clones that use 560pF capacitors in the clipping sections⁴.

The same tagboardeffects post noted that the Iron Bell "isn't based on any particular Muff circuit"², matching the maker's own account. The reviewer's overall verdict was short and positive: "Very nice and versatile take on the big muff"².

Premier Guitar, reviewing other Mojo Hand FX gear, has pointed to the company's track record with Muff-style circuits, writing that Mojo Hand FX "has impressed us in the past with their Colossus pedal's interesting interpretation of the classic Muff sound"⁵.

The controls: Volume, Tone and Color

The maker's spec lists three knobs: Volume, Tone, and Color, with Color described as a presence control¹. The two EQ knobs work together, in the maker's words, to "sculpt the overall spectrum of the EQ"¹. A retailer listing of the v3 also describes standard Gain and Volume controls alongside the Tone and Color knobs⁶.

The tagboardeffects analysis gave a practical description of how the Color knob behaves: "It works hand in hand with the tone control and will be fairly flat counter clockwise with quite a large mid boost clockwise"². For a player, that means the Iron Bell can sit close to a traditional scooped Muff voicing with Color backed off, or push the mids forward to cut through a band mix.

Tone stack values

Coda Effects published the Iron Bell's tone stack values in its analysis of Big Muff mid control approaches⁷:

• R8: 18k
• C8: 0.01uF
• C9: 0.0068uF
• C9bis: 0.033uF
• R5-1: 33k

The tagboardeffects build thread also recorded two notes from builders working from the vero layout: MPSA18 transistors at around 630 hfe were used successfully in place of 2N5089/BC550C², and a gain mod lowers the Q2 and Q3 emitter resistors (270r and 390r respectively) to 120r, or to taste, for more gain².

Power and bypass

The Iron Bell runs on a standard center negative 9V DC supply or a 9V battery, with neither included¹. At roughly 12mA of current draw¹, it is light on power, and the battery option means it can go on a simple board without a supply. Switching is true bypass¹.

The Verdigris limited edition

The Verdigris Iron Bell is a limited edition finish of the same pedal³. Mojo Hand FX lists it at $169.00³, and its specifications match the standard Iron Bell: the same Volume, Tone and Color controls with Color as presence³, the same open, rich voicing³, true bypass³, the same 9V DC center negative supply or 9V battery options³, roughly 12mA of current draw¹, and the same 4.8" x 2.62" x 1.55" enclosure³.

Like the standard version, the maker says the Verdigris circuit is not based on any particular Muff circuit but is tweaked to be a platform that is wide, yet focused³. Coda Effects counts it among the Big Muff clones using 560pF capacitors in the clipping sections⁴, so players comparing it against a vintage-accurate Muff reproduction should expect the same basic circuit family with a different midrange voicing.

Related Mojo Hand FX pedals

The maker's pages list the Iron Bell alongside several other fuzzes in the range¹:

• Colossus, based on the Russian/Civil War era Muff¹
• 1979, an op amp fuzz at $169.00¹
• Crosstown, a germanium/silicon fuzz at $179.00¹

For players weighing the Iron Bell against the Colossus, the maker's own distinction is the clearest guide: the Colossus follows the Russian/Civil War era Muff, while the Iron Bell is voiced open and rich with its own mid-shaping Color control¹.

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