GMP / Germanium MOSFET Preamp & Distortion

GMP / Germanium MOSFET Preamp & Distortion


Update: The GMP has been semi-retired while I concentrate on cool new projects. I’m leaving this page up as a resource.

The Damnation Audio Germanium MOSFET Preamp & Distortion or “GMP” started out as a simple idea to build myself a pedal that uses the similar style of distortion available in the MBD but with a focus on lower gain and more midrange to make it better suited for guitars and the mid-loving bassist. It uses Germanium diodes for their limiting properties to create a tighter crunchier clipping when mated with the MOSFET clipping stages.

A few friends got a hold of my prototypes and demanded more gain and less gain and more mids and less mids and more lows and less lows, etc. So, I cherry-picked a few of the requests worked out the version we have here. The hi/lo switch goes between the low gain version (that I originally built) and the high gain version (that my grindcoreloving friends requested). The mid is a passive midrange control that slowly adds mids back to the circuit that are cut by the distortion stages. The tone control is centered in a familiar place for those who love old tube amps. The final concession that I made (in protest) is that I lowered the pre-gain bass boost that I held onto ever so tightly (the same thing that makes the MBD-1 so massive in the low-end). Lightening up the pregain filtering was the last piece of the puzzle that truly gives the GMP its own voice.

The GMP loves vintage tube amps and modern solid-state rigs. It doesn’t care. Either way you will love how it tightens your shreds and thickens your chugs all at the same time.


Gain: Controls the amount of input gain.

Level: Controls the output level.

Tone: Tilt-style tone control centered around 450Hz.

Mid: Restores midrange frequencies.

Hi/Lo: Switches from low gain preamp mode to high gain distortion mode.


Use only 9VDC 2.1mm center negative (boss-style) power adapters. Isolated pedal specific power supplies are highly recommended. Damnation Audio pedals are designed for maximum headroom and ideal performance with a 9V supply. Going above 9VDC will damage your pedal and void any warranties. Damnation Audio pedals do not accept 9V batteries.


In the interest of continuous improvement, all specifications are subject to change without notice.

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