This pedal is a modified version of ZVEX's Box of Rock’s Distortron Engine. The improvements include a gain boost switch for added sizzle and a sub control switch with 3 levels. The amounts were carefully selected to reduce “flubbiness” that occurs when using amps with heavy low-end response. It would be immodest of me to suggest that this ZVEX effect is the greatest distortion pedal of all time, but it probably is. Try it last in your chain, and beat it up with your other effects... it stacks like a dream.