The Hiwatt Filter Fuzz MKII is a fuzz pedal launched in May 2023, described by Guitar.com as "a classic British late '60s inspired Fuzz, with upgraded features and curated filtering"1. It is a four-knob pedal whose circuit lineage goes back to Grand Funk Railroad's Messenger Fuzz, and it was released as a handwired limited edition of 201 units sold exclusively on Reverb1. Since then Hiwatt has widened the range with a V1.1 revision, a more affordable Compact version, and a Custom Shop edition2.
The sound at the heart of the pedal came about by accident. Hiwatt's master amp tech Calvin McCormick unintentionally placed a capacitor in parallel with a resistor instead of to ground, and the result became the voicing of the Filter Fuzz1. The circuit the MKII builds on is Grand Funk Railroad's Messenger Fuzz, used on the band's first three albums, including On Time2.
Controls and filtering
The Filter Fuzz MKII is a four-knob fuzz3. Its filtering is where it departs from a straight vintage fuzz: Guitar.com describes a roll-off frequency control for midrange focus and tonal options, with three filter voicings1:
| Filter position | Voicing |
|---|---|
| Filter 1 | Upper mid focus, to cut through the mix |
| Filter 2 | Mid focused, providing boost without getting too harsh or brittle |
| Filter 3 | Lower mid focused, to fill out single coils or add extra girth |
The Compact version carries its own control set: Volume, Fuzz, Filter/Focus and Thick (Bass Input) knobs, plus Filter and Fuzz footswitches2. The Thick knob is a bass input control, so it is the one to reach for on bass or when a single-coil guitar needs more weight2.
Versions: limited, V1.1, Compact and Custom Shop
The range now spans four distinct builds, at very different prices.
| Version | Build | Price |
|---|---|---|
| Filter Fuzz MKII (2023) | Handwired to order, 201 units, Reverb exclusive | £199.57 at launch1 |
| MKII V1.1 | Mostly THT components, including 2 x metal-can BC109 transistors | £189 as of June 20252 |
| MKII Compact | SMT Messenger-style fuzz, smaller enclosure | Available from Andertons and direct from Hiwatt2 |
| Custom Shop edition | Point-to-point hand-wired, large obsidian wedge-shaped enclosure | £316 / $399 as of June 20252 |
Guitar Pedal X reviewed the Compact in June 2025 and preferred it to the MKII V1.1, finding it louder and more balanced, with a pedalboard-friendly enclosure2. On the V1.1 itself, the same reviewer had one criticism:
"I really liked the pedal when I reviewed it - but felt that it was slightly underpowered on the volume side."
On the Compact, the reviewer's suggested changes were practical rather than sonic: cycling the filter options on the left footswitch, and top-mounted jacks2.
The original 2023 Filter Fuzz MKII was a limited run of 201 units sold only on Reverb1. Players looking for the same circuit new are served by the V1.1, the Compact or the Custom Shop edition2.
How it compares with other filter fuzzes
The Filter Fuzz MKII is one of several pedals that pair a fuzz with a filter rather than bolting a wah onto a fuzz circuit. The Walrus Audio Kangra Filter Fuzz, designed in collaboration with Jared Scharff from the Saturday Night Live band, gives the fuzz and the filter separate footswitches, so the filter can run independently or with the fuzz feeding into it45. The Fuzzrocious Croak Expressive Double Filter Fuzz takes a different approach: its left-hand momentary footswitch accentuates the output with a fixed, cocked-wah style effect, while the right-hand switch is bypass6. For players who want hand-wiring as a feature in itself, the Expresso FX Custom Dual Germanium/Silicon Fuzz with Filter Control is fully hand wired7.
Hiwatt itself has form with vintage fuzz: the company previously reissued the Fuzz King and Octa Fuzz, hand-built by Tone Bender designer Gary Hurst in the British Hiwatt Custom Shop.
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Questions
What fuzz is the Hiwatt Filter Fuzz MKII based on?
The circuit traces back to Grand Funk Railroad's Messenger Fuzz, which the band used on its first three albums, including On Time. The original sound came about when Hiwatt's master amp tech Calvin McCormick accidentally placed a capacitor in parallel with a resistor instead of to ground, creating the voicing that became the Filter Fuzz.
How many Hiwatt Filter Fuzz MKII pedals were made?
The original Filter Fuzz MKII was a limited edition of 201 units, available exclusively on Reverb when it launched in May 2023. Later versions, the MKII V1.1 and the Compact, were sold more widely, including through Andertons and direct from Hiwatt.
What is the Hiwatt Filter Fuzz MKII Compact?
The Compact is a smaller, more affordable SMT version of the Messenger-style fuzz. Guitar Pedal X preferred it to the MKII V1.1 for its louder, more balanced sound and its pedalboard-friendly enclosure. It carries Volume, Fuzz, Filter/Focus and Thick knobs plus Filter and Fuzz footswitches.
What does the Thick knob do?
On the Filter Fuzz MKII Compact, the Thick knob is a bass input control. It sits alongside Volume, Fuzz and Filter/Focus knobs, letting you add low-end weight to the fuzz, which is useful for bass guitars or fuller single-coil tones.
Is the Hiwatt Filter Fuzz MKII hand-wired?
The original 2023 Filter Fuzz MKII was handwired to order, with a three-week lead time between order and shipping. The MKII V1.1 uses mostly THT components including two metal-can BC109 transistors, while the Compact is an SMT build and the Custom Shop edition is point-to-point hand-wired.
Who was Calvin McCormick?
Calvin McCormick was Hiwatt's master amp tech. He created the sound that became the Filter Fuzz by accident, placing a capacitor in parallel with a resistor instead of to ground while working on a circuit, which produced the distinctive filtered fuzz voicing.
Sources (7)
- Hiwatt launches limited Filter Fuzz MKII pedal exclusively on Reverb, Guitar.com, 2023-05-18
- Guitar Pedal X, Guitar Pedal X, 2025-06-04
- Guitar Pedal X, Guitar Pedal X, 2023-05-22
- Walrus Audio Kangra Filter Fuzz, Delicious Audio, 2019-08-20
- Walrus Audio Kangra Filter Fuzz, Pedal of the Day, 2019-08-31
- Guitar Pedal X, Guitar Pedal X, 2020-12-18
- Custom Dual Germanium/Silicon Fuzz with Filter Control, Expresso FX, 2024-05-23
