Heavy Low-Ends & Prolonged Sustain
The Behringer HD300 Heavy Metal Distortion Effects Pedal is something of an odd beast in that it has no clipping section, all the distortion comes from a two-stage distortion circuit. Its heavy sound is all thanks to ingenious design features in place of a traditional clipping stage. The capacitors at the input and output of the transistor stage are not polarised enough to function properly with the input/output AC signal so this will likely add distortion, along with the emitter follower at the output of the stage due to the high level of the signal and its own slight asymmetrical bias. This is on top of the fact that this entire section itself adds some asymmetric distortion thanks to using both PNP and NPN transistors. All these factors combine to generate crossover distortion and give the HD300 its characteristic sound and distorted tones.