Another great distortion pedal from Bjorn Juhl. The EGDM is a low-medium gain hybrid overdrive. Similar in design to the Pink Purple Fuzz and Baby Blue Overdrive, it's the lowest gain of the three. In some production units, the TREBLE control is an internal trimmer. The EGDM is intended to reproduce the tones of an AC15 twin 10 amp. At low DRIVE settings, with VOICE around noon and TREBLE dimed, it is nearly clean and pretty bright. VOICE mostly controls the amount of bass feeding the distortion stage with the bass increasing as VOICE is rotated CCW. Almost all of the distortion and compression comes from overdriving a Germanium transistor (Q2) and a Silicon diode hard clipper (D1 & D2). Input impedance is high for minimal pickup loading. The EGDM is can produce over 4Vp-p at the output, which will easily overdrive any amplifier. I followed Juhl's recipe on this one, except I prefer A50K for all four pots. I'm not sure if C10 is necessary. There is a good description, a Vero layout and a link to an Andy Martin demo on Guitar Effects Layouts, April 2014. Couldn't find a good schematic, so I traced this one from the Vero layout. Try it, you'll like it.