so i had really bad buzzing from my helix lt ,no matter where i plugged in or what i used power strips etc..it was really bad when usb to pc..so yeah ground loop in house,, so i unplugged all my gear plugged my pc in with a 3 prong plug adaptor {the kind with the metal ring on it} and tried my gear everything went silent no in amps,pedals,etc...attached a wire to plug metal ring and grounded to floor... i have no problems since.......also a friend had hooked up his gear mutiple amp and stuff when he did this there was as he described a loud feed back type of sound..well after that happened he would always have a buzz when using his helix...so we took apart the helix and on the mother board you could see where he had a power surge,the board was scorched by the mono output location...so we took a small piece of wire and connected the contact points held it in place and used hot glue gun to keep it attached ...he has had no problems since ,,beeb close to year and a ton of gigs....hope this helps
