*Soundgas Type 636P 2 - Twin Grampian Preamp

Due to demand we're building 10 of these prototypes. Early preorder pricing.

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PRICE: £1,990.00 EX VAT (£2,388.00 INC VAT)



Two channel rack version of our Grampian 636 mic preamp circuit: no corners cut, all the filthy glory of the Type 636 mic preamp. Twice.

Preorders now open for a build of 10 “prototypes”. Build starts at the end of May 2022.


What is it? This is the hairy circuit you find in the mic preamp section of the Soundgas Type 636 and our desktop Type 636P. But you get it twice 🙂 . It’s based on the Grampian Type 636 – famously used and abused by Lee ‘Scratch’ Perry and Pete Townshend – and many others since. This is designed and built absolutely in the spirit of the original vintage units – no surface mount components or tone sapping DSP. Just the time and outlay to find NOS transistors good enough for the crucial parts of the circuit is slightly terrifying. 

Can I hear it? Yes! There is only one demo using the stereo version online so far (more to come). However, scroll down for many links to the desktop version in action. What you are hearing is the same circuit.

What is this “Prototype”? The photos are our working prototype: two boards from our Type 636P inside a 1U rack case. The two sides are independent circuits using a common power supply (on a standard IEC socket, internally switchable voltage). Each channel has pot to control input level, Grampian specification Mic transformer, overload lamp, input impedance switch. Staying true to the original Grampian 636 design, the output is unbalanced on a ¼” jack socket and is out of phase. We’ve simplified things a little to keep costs lower, including removing the attenuation switch on the output (they will be a little less hot on the output than the desktop version, but with no change to the sound). If we go to a full production of these we may add a faceplate and adjust the price, but we know people want this format so this is a way to crowdfund this next step in the 636 evolution…

What you receive will differ from the photos in the following ways:

  1. Most importantly, we are going to add an additional input socket for each channel to the front of the rack.
  2. The knobs will be different.
  3. It will have a serial plate.

As with our original 636s, we have put tonal considerations ahead of all else. I was skeptical that we’d see a real benefit in using germanium transistors in the buffer section: all our original prototypes had used silicon and sounded great. However Ben and Dr Huw insisted that we build an all germanium version for comparison which proceeded to blow all the earlier versions out of the water.

More info on the build of the original Type 636P including photos and demos.

To anyone reading this who has seen much cheaper versions for sale claiming they feature the Grampian ‘preamp circuit taken note for note’ we can categorically confirm that, while these units may be interesting in their own right, the circuit is certainly not an accurate recreation of the Type 636, nor do they sound at all close to either an original Grampian, or the Soundgas units. You get what you pay for. The mic transformer (one element of our design process that took a considerable amount of R&D to perfect) is not the correct value, and the circuit design means the Russian germanium transistors are not actually being driven in any meaningful way. The overdrive/distortion these units produce is not the harmonically rich germanium distortion that is the signature sound of a Grampian Type 636. We have already spent a good deal of time researching whether we could build a modern unit at a much lower price point by redesigning the original circuitry but sonically it simply does not stack up.

And if you have seen a certain guitar pedal that claims to recreate the sound of the Grampian Type 636 aux circuit as used by Pete Townshend of The Who, we can confirm that what this digital processor actually does is create a slightly boosted signal with none of the harmonic richness of the mic preamp circuitry which is what Pete actually used…


Brand new item. See notes above on how the prototypes will differ from the unit pictured.


For sales in UK the price will include 20% VAT. Buyers elsewhere may incur VAT or other local taxes on import.

Voltage Information

Will be set up for either 120 or 240v operation before shipping.

Prototype 636P2 in action


*Soundgas Type 636P 2 – Twin Grampian Preamp

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