@ simon45
Look at the plug on the end of the power cord of the NAD C315BEE. I believe it is a 2 wire 2 blade plug. Correct? No equipment ground pin. The unit has double insulated AC mains power wiring. Class II wiring.
https://www.crutchfield.com/S-OVXHs39hsLQ/p_745C315BEE/NAD-C-315BEE.html#&gid=1&pid=2
Just a guess the hum you are hearing is not a 60Hz hum. It is not a ground loop hum.
Does the hum sound like this?
https://www.youtube.com/watch?v=pf-vULfjYK8
Jim
Look at the plug on the end of the power cord of the NAD C315BEE. I believe it is a 2 wire 2 blade plug. Correct? No equipment ground pin. The unit has double insulated AC mains power wiring. Class II wiring.
https://www.crutchfield.com/S-OVXHs39hsLQ/p_745C315BEE/NAD-C-315BEE.html#&gid=1&pid=2
Just a guess the hum you are hearing is not a 60Hz hum. It is not a ground loop hum.
Does the hum sound like this?
https://www.youtube.com/watch?v=pf-vULfjYK8
Jim