If there's a hum and buzz on stage, sometimes it's just a bass player. But if it is a ground loop, you'll find DI boxes, balancers and line isolators here that can fix the problem. You can also find splitters and summers here! These little helpers solve many a tricky problem in hectic everyday stage life and should therefore not be missing from any equipment cupboard. Typical manufacturers in this area are Radial, Palmer, LD-Systems and ART. Take a look around.