In the words of The Electronic Audio Experiments:

The Electronic Audio Experiments Halberd is a discrete transistor overdrive circuit designed for the greatest possible dynamic range and note clarity. It fills a special niche our family of drive pedalsa medium-gain device with the harmonic fullness and grind of a much higher-gain pedal, one that stands apart from both the brazen buzz of op amp distortion and the smooth breakup of JFET amp emulations alike.