Posted by
Jun 24, 2019

The fruit of two years of meticulous testing and development, the Loophole Pedals Grey Matter consists in two circuits emulating the classic (and grey) ‘77 DOD250 preamp that can be run individually or stacked.

The footswitches are close enough together so you could set one as a textured boost and the other as a light overdrive or med gain distortion and switch between them by stomping ONCE. Not to worry, they’re far enough apart to easily stomp the switches individually as well.

Each channel features knobs for GainEdge and Volume – with the second one controlling diode saturation – and a three-way toggle switch called Sense, which “set the hard clipping diodes placed after the gain section”:

  • The toggle down position honors the original silicon diodes of the grey 250 with symmetrical clipping for a balanced distortion.
  • The toggle up position utilizes one of two of my favorite clipping personalities (the blue side equips Bat41 Schottky diodes and the green side has 1n270 germanium diodes); this also uses symmetrical clipping.
  • The middle position bypasses the hard clipping stage & edge control knob for simple folk who wanna just drive the LM741 op-amp naturally.

Here’s the video by 60 Cycle Hum

I started designing GREY MATTER from a skeleton of the vintage grey version, ‘77 DOD250 preamp (hence the name.) I made many improvements for stability and tone and added edge control for hard clipping saturation. The overall project took two years of meticulous testing and development before I was satisfied with the jaw-dropping result.

2 Drives In 1 Enclosure

Initially, I was going to have only one 250 based drive in the housing, but I noticed the unit sounds amazing stacked into another one of the same…so there are two individual circuits in there. Run ‘em individual or stacked! The footswitches are close enough together so you could set one as a textured boost and the other as a light overdrive or med gain distortion and switch between them by stomping ONCE. Not to worry, they’re far enough apart to easily stomp the switches individually as well.

Sense and Edge Control

There are two sense toggles with 3 positions each for a total of 6 senses. The switches set the hard clipping diodes placed after the gain section. I committed to two unique sets of diodes on each side. The toggle down position honors the original silicon diodes of the grey 250 while the toggle up position utilizes one of two of my favorite clipping personalities (the blue side equips Bat41 Schottky diodes and the green side has 1n270 germanium diodes); both positions use symmetrical clipping for a balanced distortion. The middle position bypasses the hard clipping stage & edge control knob for simple folk who wanna just drive the LM741 op-amp naturally. The edge control acts to control diode saturation. Edge at 9oclock will produce first to second stage gain tones, while heavier tones result with the edge at 3oclock.

Components

The GREY MATTER is 100% analog using respected components; Lumberg audio and power jacks, mini 3PDT for a shorter & more controlled soft click, WIMA caps, etc. GREY MATTER is handmade in Texas.