Originally produced in 1975 as a relative of the famous Small Stone, the Electro-Harmonix Bad Stone took phasing to the next level with the addition of the manual shift knob, which allows you to find your filtering sweet spot. Although Electro-Harmonix produced a two-knob version of this pedal with just the rate and feedback controls, the three-knob examples give you more control over your tone and are thus more highly sought.