Hi, i've got three pedals powered off one 9V supply and a daisy chain power adaptor, a clever little thing that plugs into the end of the supply and offers five 9V outputs, the only thing is that whenever i use it with more than one pedal a big electrical buzz occurs, even if all the pedal are set to clean. The bass can still be heard but not well over the buzzing. is this a problem with the daisy chain or should i buy a power supply for each pedal?