It's our reissue of the legendary Colorsound "Power Boost" (18v), later renamed "Overdriver" but then powered with 9v. Among the players that used this legendary gadget back in the seventies there were David Gilmour, Jeff Beck or Marc Bolan. The Pro Boost is a very versatile pedal that can be used for a variety of purposes. It has plenty of clean output volume so it can be used for a volume boost (if there's enough clean headroom in the amp) or it can be used to crank the valves of any amp. But the Pro Boost is also a powerful distortion pedal. A master volume was added so the original volume knob can be used now as a gain knob making available all the distortion capability of the circuit at any output volume. The cranked sound of the Power Booster-Overdriver could be classified as "distortion" rather than "overdrive" or "fuzz"; it's a very characteristic quacky and raspy sound with a nice clean up through the guitar's volume knob. I build the original 18V circuit which provides more headroom; it can be powered with 9V as well.
