The Eau Claire Thunder is a fuzz and distortion pedal made by Dwarfcraft Devices, a pedal builder based in Eau Claire, Wisconsin. Delicious Audio called it "the big one" from the company, and Delicious Audio later described it as the pedal that put the Wisconsin builder on the map in the early aughts12. Premier Guitar called it Dwarfcraft's flagship distortion device and its best selling distortion device for bass, guitar, and everything else34.
What sets it apart from most Muff-style boxes is a built-in feedback loop on a momentary footswitch, which lets the pedal self-oscillate on demand1. At its core, though, it is a standard volume, tone, gain arrangement yielding a distortion that Delicious Audio found much less tubby and bouncy than a typical Big Muff1.
A Muff-flavored distortion with a built-in feedback loop
The circuit traces back to the Big Muff. Coda Effects' technical analysis of the Big Muff circuit notes that the tone stack can even be removed, giving an "in your face" sound with a lot of midrange, and that this approach appears on the Eau Claire Thunder6. That is exactly what the pedal's Toneblast footswitch exploits: it removes the tone stack from the circuit for unfiltered distortion1.
The 2019 limited edition went further toward vintage territory, using germanium diodes and NOS Fairchild 2n5133 transistors for what Premier Guitar called a vintage Muff vibe3. Because of the choice of transistors, only 65 of those units were built3.
On the sound, Delicious Audio's 2012 review was direct:
"This pedal cranks out all manner of fuzz from the blunted, smokey kind of Sabbath style fog to the much more modern aggressive waves of noise rock bliss."
The pedal has been used by many players, including Takeshi Ohtani of the Japanese band Boris5.
The controls
The original Eau Claire Thunder carries five knobs plus toggles and extra footswitches, and Delicious Audio found them deeply interactive: "The five knobs on the pedal's face seem infinitely interactive and changing one leads to variations in the way they combine"1.
| Control | What it does |
|---|---|
| Volume, Tone, Gain | Standard Muff-style arrangement setting level, tone and distortion amount1 |
| Feedback Tune knob | Tunes the internal feedback loop's oscillation frequency1 |
| Feedback footswitch | Momentary switch that engages the internal feedback loop12 |
| Timewarp toggle | Switches between two different sets of clipping diodes, changing the pedal's attitude from vintage to modern13 |
| Toneblast footswitch | Removes the tone stack from the circuit for unfiltered distortion; bypassing the Tone control gives more volume and a fuller frequency response13 |
The Gold Standard edition reorganized the control set: gearnews listed a Volume, Tone, Trim and Distortion knob set, plus a Time Warp switch and a regular Bypass and a Tone Blast footswitch7.
Limited editions: Gold Standard and the Boris run
The Eau Claire Thunder has appeared in several limited versions over the years.
| Version | Year | Run size | Key differences |
|---|---|---|---|
| 2019 limited edition | 2019 | 65 units3 | Smaller enclosure, top mounted jacks, no feedback circuit, germanium diodes, NOS Fairchild 2n5133 transistors3 |
| Gold Standard | 2019 | 73 units78 | Smaller streamlined enclosure, Timewarp toggle, Toneblast switch, $229 retail38 |
| Gold Standard (2020 run) | 2020 | 70 units2 | Stripped of the feedback loop section, vintage hand-sourced components2 |
| Boris run | 2020 | 40 units, twenty of each design5 | Screen-printed art of Boris' LOVE or EVOL albums5 |
The Gold Standard, announced in 2019, was described by Guitar World as an update of the flagship Eau Claire Thunder with a smaller, streamlined enclosure and control interface8. Its circuit differs from the standard version: the use of NOS transistors decreased the gain, making it, in the builder's words relayed by Premier Guitar, warmer, a little more "wooly," and somewhat more versatile than the balls-out OG Thunder38. Gearnews similarly found the gain lower than on the standard version, a "warmer" circuit that's a touch more "woolly"7. Delicious Audio reported the builder describing it as not as extreme as the original, but more detailed and "woolly"2.
The 2020 Gold Standard run was more compact and streamlined still, stripped of the feedback loop section, the Feedback footswitch and the Feedback Tune knob2. Gearnews' writer predicted the 2019 run would not linger: "I have a feeling that these will sell out really quickly and probably end up on Reverb being sold on at a premium"7.
The Boris run of 2020 came in two versions, each featuring screen-printed art of either Boris' LOVE or EVOL albums, with 40 units in total, twenty of each design5. The Gold Standard carried a $229 retail price in 20193, and gearnews listed the Boris-run pedals at USD 279 RRP in 20205.
The Baby Thunder and the smaller formats
Dwarfcraft has also offered the circuit in a compact form. Guitar Pedal X's reviewer, Stefan Karlsson, wrote that he had owned the compact Baby Thunder for several years and had always intended to get the vertical 1590BB enclosure Gold Standard Edition9.
The Gold Standard edition is a separate product from the original Eau Claire Thunder: it drops the feedback loop, uses different components, and was built in limited runs. See the Dwarfcraft Eau Claire Thunder Gold Standard page for that version's details.
Where the name comes from
The pedal is named after the bad weather of the company's hometown, Eau Claire, Wisconsin5. The 2019 limited edition came from what Premier Guitar called a brilliant idea by Dwarfcraft's Supreme Commander Louise3.
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Questions
What does the Timewarp toggle do on the Eau Claire Thunder?
The Timewarp toggle switches between two different sets of clipping diodes, changing the character of the pedal from vintage to modern. Premier Guitar describes it simply as a toggle that controls a clipping diode, while the original Delicious Audio review found it shifted the pedal's attitude between vintage and aggressive modern fuzz.
Is the Eau Claire Thunder a fuzz or a distortion?
It sits in both camps. Delicious Audio reviewed it as a fuzz and distortion pedal that cranks out everything from smoky Sabbath-style fuzz to aggressive modern tones, while Premier Guitar called it Dwarfcraft's flagship distortion device. The circuit is Big Muff-derived, which is why it gets described both ways.
Does the Eau Claire Thunder work on bass?
Yes. Premier Guitar described the Eau Claire Thunder as Dwarfcraft's best selling distortion device for bass, guitar, and everything else, and gearnews reported it has been used by many players including Takeshi Ohtani of the Japanese band Boris.
What is the difference between the Eau Claire Thunder and the Baby Thunder?
The Baby Thunder is a compact version of the same circuit in a smaller enclosure. Dwarfcraft reintroduced it in November 2016 alongside the SheFuzz as a smaller-enclosure reissue with new controls. Guitar Pedal X's reviewer owned the Baby Thunder for years before picking up the full-size vertical 1590BB enclosure Gold Standard edition.
Where does the name Eau Claire Thunder come from?
The pedal is named after the bad weather of Dwarfcraft Devices' hometown, Eau Claire, Wisconsin, according to gearnews. The company is based in Wisconsin, and the Eau Claire Thunder is widely described as the pedal that put the builder on the map in the early aughts.
How many Gold Standard Eau Claire Thunders were made?
Reports differ on the run size. Guitar World and gearnews both said 73 units worldwide in 2019, while Delicious Audio later described a limited run of 70 units in 2020. The 2019 limited-edition Eau Claire Thunder that preceded the Gold Standard was capped at 65 units because of its NOS Fairchild 2n5133 transistors.
Sources (9)
- Pedal Review: Dwarfcraft Devices Eau Claire Thunder, Delicious Audio, 2012-01-12
- Dwarfcraft Devices Eau Claire Thunder Gold Standard, Delicious Audio, 2020-04-27
- Limited-Edition Eau Claire Thunder by Dwarfcraft, Premier Guitar, 2019-05-29
- Dwarfcraft Reintroduces Baby Thunder & SheFuzz Pedals, Premier Guitar, 2016-11-16
- Dwarfcraft Devices closes down, issues special Eau Claire Thunder fuzz pedals, gearnews.com, 2020-04-20
- Coda Effects, Coda Effects, 2026
- Dwarfcraft Gold Standard Eau Claire Thunder: A limited run of only 73 units, gearnews.com, 2019-06-03
- Dwarfcraft Unveils New Eau Claire Thunder Gold Standard Distortion, Guitar World, 2019-05-30
- Guitar Pedal X, Guitar Pedal X, 2025-11-12
