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The New of Aclam:
The Windmiller Preamp

Push your amp to its raw power!







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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.

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]

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.


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!


We have done it again: The Windmiller Preamp

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.


The Windmiller Preamp pedal

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

Download The Windmiller Preamp's user manual