The ABY Switcher allows you the ability to switch between 2 output or switch them on together. If your setup is 2 amps, plug your amps into A and B then you can switch the output between the 2 or run them both at the same time. This is an ABY switch which lets you send your input to either the A or B outputs, or to both simultaneously. The pedal is powered via the 9v Boss style 2.1mm DC socket (centre negative).