Aclam Windmiller

The Aclam Windmiller is a preamp pedal and booster from Aclam, the Barcelona-based maker better known for its Smart Track pedalboards. It is a faithful recreation of the preamp section of the Grampian Reverberation Unit Type 636, serial number 1138, a spring reverb unit whose preamp Pete Townshend of The Who used in the mid-'60s as a saturation tool, with no reverb at all, to crush the input of his Marshall amps¹²³. Aclam describes the result as a vintage gritty tone, both clean and overdriven, usable to boost the guitar signal, push an amp or overdrive pedals, or run with a light touch of gain⁴.

Aclam matched the critical low input impedance of the original Grampian and reproduced much of its topology, but with a heavily improved signal-to-noise ratio and increased treble response, plus EQ controls the original never had, so it can be matched to guitar and amp combinations other than Townshend's own setup⁴².

The controls

The Windmiller's knob layout mirrors the vintage Grampian, though the control functions are not the same⁷. Where the original gave you fixed behavior, the pedal gives you shaping:

The Gain knob is the heart of it. Aclam says that as you turn it up, it drives the amp's preamp to increase saturation¹. Guitar World's reviewer, Trevor Curwen, noted that with the Gain at minimum there is already a small level boost and an instant tonal shift when you kick the pedal in, and that turning it up produces drive that cleans up naturally with the guitar volume, calling the tone controls "Practical tone controls" and a reason to buy⁵.

Premier Guitar's reviewer found the EQ flexible enough for guitars and amps far from Townshend's recipes, and described the pedal's character in use: open, airy tones, a scooped, substantial and smooth tone shift, distinct compression as gain advances, and a top end that gets excited without turning brittle. Set against a favored germanium boost, that boost "sounded a bit narrow and harmonically constrained in relation to the Windmiller's open, airy tones"².

Power and connections

The Windmiller runs on a 9V DC center negative power supply with the standard Boss type 2.1mm connector, and draws approximately 38mA; Aclam specifies a supply rated 100mA minimum⁴⁶. There is no battery option; the unit must be powered by a supply⁸.

Connections are simple: one input jack and one output jack⁶. The pedal uses relay true bypass switching, so when it is off, the signal is switched out of the circuit entirely rather than passing through it⁴. Guitar World's review confirms the true bypass and also notes the pedalboard fixing system⁵.

History and versions

During development the pedal went through changes. Early prototypes used germanium transistors, then silicon transistors, which had more treble response but were still noisy; Aclam's designer, Marc Sospedra, has written about the process, and the pedal was at one stage called the "Grampian Overdrive"⁷. The finished Windmiller keeps the vintage unit's look, including the overload lamp, while adding the Hi-Cut and Lo-Cut controls the original lacked⁴³.

The Windmiller sits in a series of Aclam pedals that replicate classic guitar tones, alongside the Cinnamon Drive and the Dr Robert⁹. Guitar World's reviewer characterized the company as having "a nose for seeking out obscure, perhaps forgotten, but crucial gear and resurrecting it"⁵.

Versions and availability

• The Windmiller Preamp: the standard version, in a custom light aluminum enclosure designed to fit Aclam's Smart Track pedalboards, with an anti-sliding rubber pad and a Velcro pad included⁴⁸.
• Scratch & Dent: fully functional and tested to the same standards as regular products, possibly with small scratches, smudges on the screenprint, powder coating defects, or as demo units used for reviews, with the same warranty and next day shipping¹⁰.

As of October 2026 the standard version is listed at Aclam's store, which offers email notification for updates on the pedal⁴.

Warranty

Aclam's product page states a lifetime warranty⁴. The 2023 manual, meanwhile, describes a two-year warranty from the purchase date under current Spanish legislation, not transferable, with claims requiring proof of purchase and the serial number, returned to the store within one month of discovering the fault⁸. The two documents disagree, so check which applies before relying on either.

What reviewers said

Premier Guitar's reviewer, comparing it against a range of alternatives, concluded that "playing the Windmiller alongside a bunch of overdrives, boosts, and preamp pedals reveals a unique responsiveness and palette of sounds"². The same review noted the price: "The Windmiller is expensive for a preamp pedal at $310"².

Guitar World's Trevor Curwen highlighted the practical tone controls as a buying reason⁵, and Delicious Audio described the design goal behind the EQ: "we challenged ourselves to make this preamp sound beautiful no matter what amp or pickup you use"³.

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