[size=4]There are two versions, the original with a slight low and high end pre-shaper built in, and a flat response unit, where the controls are set in their most neutral setting, there will be no coloration, or difference in response, when switching between active and passive. The pre-shape unit gives a slight lift and fatness when switched in, whereas the flat response type retains the original sound, except that the pickups are buffered by the preamplifier.[/size]