I have hardwired speakers attached to my receiver and when I play radio stations from the receiver, I have no buzzing issues, but it occurs when the TV and cable box are on. Since I have Directv I read previous posts and assumed I had a ground loop problem so I purchased an isolation transformer and connected it to the coaxial cable which then attaches to the cable box. The connector from the box to the TV is not coaxial.
The speakers and TV are on one wall with the receiver located on a different wall about 10 feet away.Now the only time I get the buzzing is when I walk between my receiver and my TV and speaker wall. If I avoid “breaking that plane” there are no issues even with the TV/cable box on. It’s almost like what happens when you have an antenna but there is no antenna.