T-Rex Mudhoney

The T-Rex Mudhoney is a distortion and fuzz pedal with a wide tonal range, and one of the first pedals T-Rex produced¹. Its core idea is simple: with the boost switch off it delivers what T-Rex describes as "a full range of sweet sounding overdrive", and kicking the boost on takes it to what the maker calls "a whole new level of searing distortion"¹. T-Rex describes the result as raunchy-but-smooth distortion, with a slightly aggressive and punchy midrange that can be almost fuzz-like on high gain settings².

The pedal has four knobs and two switches: on/off, level, gain, tone and boost¹. The gain knob controls the distortion amount, the level knob sets overall volume (1:1 at twelve o'clock, up to a 15 dB boost fully clockwise), and the tone knob shapes the top end of the signal³. The boost button switches between moderate and high gain³.

What the boost does to your sound

With the boost bypassed, the Mudhoney delivers moderate gain and a smooth, rich sound that, according to the technical analysis on Guitar FX Layouts, many jazz guitarists favor³. A builder who assembled the circuit from a stripboard layout found the boost-off setting "very thick tone with warmth that could quickly find its way to being your main dirt for jazz, blues, etc."³

Engaging the boost is a different animal. The same builder, hitting it with a Les Paul bridge pickup, reported sustain "of Spinal Tap proportions" and chords that were "a menacing wall of sound but yet unlike its name would imply, the Mudhoney didn't get muddy and muffled"³. Note and harmonic separation held up too, "giving a very dimensional sound at gain levels where most pedals sound flat"³.

On That Pedal Show, Mick found that switching the boost on put him in mind of a whole other pedal, a demo that also covered other T-Rex pedals including the Replicator⁴.

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A modified Rat circuit

Independent circuit analysis of two traced Mudhoney schematics concluded that "they're both obviously modified Rats", with variations in component values possibly reflecting different versions of the pedal³. A later analysis on the same site called it a tuned Rat, noting that instead of the Ruetz-style mods on the Rat, a builder can get the Mudhoney tone from a stripboard⁵. The circuit keeps BJT transistor buffers (BC546B) close to the original topology, with the electronic switching removed to accommodate true bypass in the reissue⁵.

One reviewer who built and compared it described it as "a nice sounding Rat variant. It is quite dark though. Using a C taper 100K seems to remedy that issue. It cleans up better than a stock Rat does, even on the dirty side", and found it sounds similar to a Rat or Rat 2 with a touch of Ruetz mod tone⁵.

The gain section has a 150R resistor from pin 2 to the gain pot, with the other side of the pot at pin 6 and a 100p cap in parallel between pins 2 and 6; the 150R sets minimum gain and the pot value sets maximum³.

Versions: original, DK reissue and Mudhoney II

The Mudhoney line has taken a few forms:

The Danish-made reissue has been around since 2018, and Guitar.com's Richard Purvis, reviewing another T-Rex pedal, wrote that he is "a big fan of the Danish-made reissue of the Mudhoney distortion, which has been around since 2018, so this neatly designed green metal box certainly has pedigree"⁷.

The Mudhoney II, announced by T-Rex in June 2010 alongside the Octavius, is described by the maker as "everything that is great about the original Mudhoney, and then doubles it": two channels of vintage gain, each with its own gain, level, tone and boost controls, and the ability to deliver everything from a smooth dirty edge to a harrowing wall of distorted sound⁶⁸. Circuit analysis suggests it is more or less two Mudhoneys, possibly with slight differences⁵. T-Rex's webshop lists the Mudhoney 2 as sold out⁹.

Power and bypass

The Mudhoney runs on a 9V DC supply (T-Rex recommends its FuelTank), accepting 8V DC minimum to 12,5V DC maximum, and draws only 6 mA at 9V DC, so it is easy on a pedalboard power supply¹. It also takes a 9V battery (6F22) good for 14 to 18 hours¹. Maximum input signal is 1,5V p-p³.

Building a clone from a stripboard layout

Guitar FX Layouts published a stripboard (vero) layout for the Mudhoney in June 2012, traced from a freestompboxes schematic, and a builder verified it using substituted parts (BC547 and LM308 transistors in place of the originals)³. In January 2023 the schematic was re-traced by Kasper from his V1.1 pedal, after earlier DIY builds reportedly did not sound right, possibly due to faulty schematics circulating online⁵. That re-trace produced a new V1.1 layout, and a V2 revision that incorporates a 47R CLR for the power supply and a 10K pulldown at the output, matching the later schematic revision³⁵. The V2 layout also adds a 1M pulldown resistor at the signal input, not in the original schematic, to reduce popping when switching⁵.

One practical note from builders: the gain pot taper jumps from almost nothing to almost full blast right at the beginning of its rotation, and a 100k log pot gives a near perfect taper³.

Related T-Rex pedals

Players comparing dirt pedals in the T-Rex range may also want to look at the Dr. Swamp, the TwinBlaze, the Mean Machine, the Dual Drive and the ToneBug Totenschlager, or browse overdrive and boost pedals more broadly.

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