Running your effects pedals off a battery can be expensive. Especially if you forget to unplug your guitar lead when you finish playing. The battery will be drained! This is where the Guitar Man GMP02 9 volt power supply comes in. It is DC, 600ma. It will happily power your effects pedals. Good quality yet very reasonably priced. Perfect if you run a single stomp box set up or need a 9v power supply for a multi effects unit.