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The Windmiller Preamp

Push your amp to its raw power!


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 color, a booster for solo parts, or a tool to saturate and enhance the amp's natural overdrive.

✔  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






Aclam demo


Youtube demos



The Windmiller Preamp audio samples

Preamp Color

Amp: Marshall JTM45 Normal Channel Vol. at 2 Eq flat W/ 4X12 GREENBACKS
Guitar: 1963 Fender Stratocaster Bridge Pickup

Pedal bypassed

Pedal on

Vintage Grampian Tone

Amp: Marshall JTM45 Normal Channel Vol. at 2 Eq flat W/ 4X12 GREENBACKS
Guitar: 1963 Fender Stratocaster Bridge Pickup

Pedal bypassed

Pedal on


Bass cut w/no boost

Amp: Marshall JTM45 Normal Channel Vol. at 2 Eq flat W/ 4X12 GREENBACKS
Guitar: 1963 Fender Stratocaster Neck Pickup

Pedal bypassed

Pedal on

Broken amp tone

Amp: Marshall JTM45 Normal Channel Vol. at 2 Eq flat W/ 4X12 GREENBACKS
Guitar: 1963 Fender Stratocaster Neck Pickup

Pedal bypassed

Pedal on


Amp saturation and creamy tone

Amp: Marshall JTM45 Normal Channel Vol. at 6 Eq flat W/ 4X12 GREENBACKS
Guitar: 1963 Fender Stratocaster Neck Pickup

Pedal bypassed

Pedal on

Bass cut action at full boost on a cranked amp

Amp: Marshall JTM45 Normal Channel Vol. at 6 Eq flat W/ 4X12 GREENBACKS
Guitar: 1963 Fender Stratocaster Bridge Pickup

Pedal bypassed

Pedal on



Get inspired with The Windmiller Preamp's playlist


What's said?

Users reviews

What customers think about our products?


You´ll get that Townsend grit instantly... Buuut there is much more in this pedal. Its build Quality, Arts, Details and information are great, YOu get 2 pedals in one: please read de instructions about impedance.

Alfredo L. - 16 Jan. 2023

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The second best pedal I have.

The best pedal I have is the Dr. Roberts. This is almost as good. Both are absolutely fantastic and do exactly what they promise. I saw one comment that said it was not good at bedroom level but I had no problem at...

John d. - 18 May 2021

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Listen, this pedal gives you the growl to devour all these phony baloney guitarist. I cant tell you how much i love this thing. Buy it, you wont regret it

James M. - 30 Apr. 2021

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i was excited to receive my windmill Preamp! so i plugged it into my pedal board directly after my guitar as the fist pedal followed by a compressor and then my various pedals. i'm experiencing some clipping when...

tom c. - 28 Apr. 2021

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Media reviews

Pete Townshend's Power-Pop Propulsion Secret

"I love the way the Windmiller's harmonic profile excites a guitar's top end without making it brittle."

Premier Guitar (Premier Gear)

Read this review 

Another excellent, meticulous and precise re-imagining of a classic circuit.

“Since The Windmiller Preamp and the original Grampian 636 were designed as studio tools, you can use it on guitar, bass, keys, etc….the sky’s the limit here!”

Pedal of the day

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Guitar world logo

"Practical tone controls and quality footswitching, Pete Townshend’s secret '60s sound-shaper revisited in pedal form"

"A Strat and The Windmiller into a vintage Marshall JMP50 gave us that classic Townshend sound: edgy raunch with an open clarity that’ll entice you to play chord-driven Who songs of the period such as Substitute or I Can’t Explain."

Guitar World

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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

"It is a great pedal to thicken your tone. I’ve been testing it with a Fender and it works great, it is like I’m adding the preamp of another amp.”
Vicen Martinez


“It is very useful in the studio, as you have a wide range of possibilities with minimal controls. I like the color it adds, and the frequency cuts are very useful. A perfect variety of saturations.”
Jordi Bastida

“More than just a booster, a sound thickener. It could be said it turns single coils into humbuckers. Sweeter tone with less sharp percussive attack. The lo cut is totally necessary, specially when using humbuckers.”
Roman Gil


Tech Specs

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 requirements9V DC Center Negative 100mA minimum
Current draw: ≈38 mA
 Included: 1 x Anti-sliding rubber pad & 1 x Velcro® pad

Download The Windmiller Preamp's user manual



Choose the best chain position for The Windmiller Preamp

Due to its low input impedance, the location of this versatile preamp on the effects chain is crucial to get the desired functionality. Here’s some practical examples that will help you out to find the best setup for your beloved The Windmiller Preamp.

Townshend Setup windmiller

Townshend Setup

The Windmiller Preamp receives the signal directly from the guitar output Jack.

The result is the same as Townshend’s rig: Tone coloring and as you turn the Gain knob up drives the amp’s preamp to increase saturation

Preamp with tone coloring windmiller

Preamp with tone coloring

The player gets the 636 tone coloring but the signal boost can overload the following pedals before the amp.

This is really interesting for overdrive pedals, in order to get new textures from them.


Preamp with no coloring windmiller

Preamp with no coloring

The Windmiller Preamp pedal gets the signal from a buffered pedal it changes its behavior.

It becomes a transparent preamp. Use it to add gain to the following overdrive pedals but the tone will not be “colored” anymore.

It will be a louder version of the bypassed signal. Use the eq controls to shape and fine tune your tone.

Transparent and linear boost windmiller

Transparent and linear boost

The Windmiller at the end of the effects chain will act as a regular booster: Louder signal with the less tone coloration possible.

There is a lot of chances that some buffer or effect circuit will be placed before the Windmiller Preamp (Isolating the pickups and, at the end, converting the signal to low impedance.)

The Windmiller Preamp will react as a transparent booster without adding its color. We found this ideal for solo parts or to recover some gain after all the effects chain


A short story about this pedal







It all started on a lazy Sunday, surfing through YouTube looking for some old footage of The Who, when we stumbled on some clips of The Who playing at the Marquee Club in 1967. Despite the raw energy of those four young men, what really caught our attention was a weird device with a flashing light sitting on top of Pete Townshend’s Marshall amps.





After some research 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.

Grampian 636 Reverb unit

“I use a Granpiene [sic] reverb unit for distortion; it gives a kind of clear fuzz dirge. I like a slightly broken guitar sound.”

[Pete Townshend. Guitar Player interview in 1967]





With that amazing story on the table, it was clear it could be something for Aclam’s team to work on!

So, we were really decided to create a pedal version of the 636 preamp but we had a slight problem, we had never tried one. So, in order to recreate it to the finest detail we began our search for an original unit that we could reverse engineer. After many months we managed to get our hands on an original Grampian unit! It was in a great shape and sounded amazing!

As soon as we strummed the first chords with the original 636, we found the combination of Grampian, old Marshall stack and single coils to be pure magic. It enhanced the amp’s natural saturation with a fatter, sweeter tone. This unique coloring comes out of its primitive technology and because of the low input impedance of the 636. This is also quite common on guitar effects of that era, like the Fuzz Face®, Range Master and many other 60’s effect units.

However, we felt the vintage 636 was less impressive when used with other types of amps and pickups, specially humbuckers. Because of that, 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 behavior 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!

Marc and Marcel interview




Get featured

If you ahve a Windmiller Preamp effect pedal, tag your videos & pictures with the hashtags #windmillerpreamp & #myrigmyrules in social media to get featured!



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