HAO's ultimate overdrive unit, creates characteristic overdrive that is unheard of before. When a mini switch is set to "Boost" position, Rumble MOD functions as a booster and amplifies input signal so that a player can vary the signal strength with pick attack from crystal clean to crunchy overdrive. In "Drive" mode, depending upon setting of "Color" control, Rumble MOD generates from fat and silky to edgy and sizzling overdrive. This "Color" control works opposite of regular tone control and acts as a type of filter control on significant frequency ranges.