It is a different set of circumstances, but I believe that this might be helpful for people experiencing ground loop problems. I am rocking it old school vinyl. Classic Dual turntable grounded to a Sherwood receiver. The left side of my Eris 3.5 speaker family wasn't happy until I realized that the turntable didn't have a grounding plug. I simply went to the kitchen, picked up my heavy duty grounded extension cord that has 3 grounded heads on the business end. Turntable, receiver and speakers all on the same cable. Problem solved. No hum or feedback at any volume. No ground loop isolator required. I recommend targeting the power supply by providing a heavy duty ground and try to solve the problem here instead of at the RCA etc input level. Hope this helps and saves people lots of money!