The Windmiller Preamp

Grampian Reverberation Type Unit 636 S/N: 1138

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

“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 

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. 

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 Overview 5 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!

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.
 

 BYPASS SWITCH

Engages the unit allowing the signal to flow through The Windmiller Preamp circuit. It also lights up the LED above it. GAIN: This control lets you set the amount of signal boost of the instrument you plug into it. At counterclockwise position will increase around 3dB’s (depending on the settings of the Lo. Cut and Hi. Cut knobs) compared to the bypassed signal. As you start to turn the Gain up, it’ll build up more volume just like a regular preamp or booster. Please bear in mind this is a “clean” preamp meaning it doesn’t add saturation per se (a little bit of asymmetrical clipping with the Gain fully clockwise though) but will clip any following device after it like an overdrive pedal or the amp.

OVERLOAD LIGHT

 We felt we needed to pay tribute to the vintage Grampian 636 by including the Overload indicator light! In this pedal version it only serves as a “signal in” indicator, although the higher the gain and the harder you play, the brighter it will glow as it reacts with the signal dynamics.

LO CUT

When using The Windmiller Preamp a la Townshend style (to saturate your amp) you may find the resultant overdrive is a bit fuzzy. This is not necessarily a bad thing, but we have found useful to include this Lo. Cut control to reduce bass content and make mid frequencies pop out a bit more. When it is fully counterclockwise it will reproduce the entire bass frequency spectrum (like the vintage Grampian 636) and as you start turning it clockwise, low frequencies will drop. This control is meant to be a fine tune, so it doesn’t have a drastic effect like many eq’s found on other pedals or amps.

HI CUT

The vintage 636 tone is perfect for single coils because it tames its high end and makes it sound slightly round and mellow, just the perfect amount. But on the other side, we found that humbuckers were a bit unhappy with that. For this reason, we made The Windmiller Preamp brighter than the 636 and included this Hi. Cut control so it is more versatile with any kind of guitar and pickup. Fully counterclockwise is the brightest position, ideal 4 7 8 13 for darker pickups and as you move the knob it will remove highs until the fully clockwise position where it is enough to tame the brightest pickup.