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Aclam Windmiller Preamp Pedal

Modelled beautifully after an original Grampian Reverb Unit


Here's what Aclam say about the Windmiller Preamp:

An effect pedal that recreates the Grampian Reverberation Unit Type 636 S/N: 1138 Pete Townshend used as a saturation tool. The result is a versatile pedal that can be used as an 'always on' preamp with a beautiful colour, a booster for solo parts, or a tool to saturate and enhance the amp's natural overdrive.

Key Features

  • Based on the preamp of the Grampian Reverberation Unit Type 636 S/N: 1138
  • Suitable for guitar, bass and keys
  • Improved and quieter circuit including true bypass switching
  • Hi. Cut and Lo. Cut tone shaping controls for maximum versatility
  • Smart Track® Fastening System


We found out that between ‘66 and ‘67, Pete Townshend had several Grampian 636 Spring Reverb units in his arsenal and he used them as a saturation tool, cranking his Marshall amps to the limit to get his groundbreaking tone.
Even though it was intended as a studio reverb unit, Pete used the built-in preamp of the 636 to fatten his tone and boost the guitar signal, bypassing the reverb altogether. Since Pete used it for a short period of time, it ended up forgotten and only the erudite of The Who knew the story of the 636.

We challenged ourselves to make this preamp sound beautiful no matter what amp or pickup you use, managing to eventually tweak the circuit to extend its frequency range and include eq controls while retaining its unique tone. The treble response has been refined by adding a Hi-Cut control which allows you to add a sweet sparkle to muddy humbuckers or tame brighter single coils, as well as a Lo-Cut knob to control bass content better, so the player can decide the tightness of the resultant tone.

Another thing we achieved was to refine its background noise. The vintage Grampian has a remarkable hiss, especially when the Aux Channel was used (Townshend’s choice). Chapter two of the Windmiller designing process was to eliminate that hiss whilst maintaining the character and behaviour of the original Grampian 636 preamp. After experimenting with a great variety of components and fine-tuning the circuit to make it as quiet as possible, we finally succeeded!

And finally, in order to pay tribute to the last detail, we’ve included the overload indicator lamp found on the Grampian 636, which is sensitive to your playing and responsive to your attack, and you may agree with us, looks really cool!

Musician's reviews

“I do not use many effects pedals and the tone I’ve attained with my amp and how it interacts with the guitar has blown me away. It can bring any amp back to life!” - Marc Argenter

“It has achieved to create a natural distortion coming out of the amp that I really like, very much like the British mid-sixties feel of Clapton, Page, Townshend… When you crank up the volume it carries me to the power chord vibe of that time.” - Vidal Soler

“I would keep this pedal engaged all the time! When you experiment with different guitars you can notice how it gets the most out of the different pickups. Not to mention when you increase the volume and how that affects the guitar’s tone and pickup response.” - David Soler


  • Dimensions: 13,6 x 8,7 x 5,5cm (5,4” x 3,4” x 2,2”) with knobs
  • Weigth: 450 gr. (1 lbs)
  • Bypass: Relay True bypass
  •  Power requirements: 9V DC Center Negative 100mA minimum
  • Current draw: ≈38 mA
  •  Included: 1 x Anti-sliding rubber pad & 1 x Velcro® pad
Inc. VAT

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