At a gig last night the outlets where not grounded. So the two guitars had that "hum". The owner of the bar said that most of the bands that play there bring in a "power box" that is on fifty or so feet of wire with eight plugs on it. They pull it right out of the main power box. This all sounds very cool-is it? and how does it hook up and how hard is this to make? can you buy them? thanks to all who help!