McIntosh MC205 hum

My McIntosh MC205 hums. It is set up with all the proper interconnects and I use a Krell HT Standard as the processor. It hums and is a bit annoying. Is this natural? I went back to my dealer and they said I had improper grounding. It is plugged into a surge protector which goes into a 3 prong wall outlet. The surge protector indicated protected but not grounded. I have an old house. There are walls that I've opened elsewhere in the house and there ground wires running from the box. So I bought a green ground wire and grounded the wall outlet to the box. Surge protector still did not show grounded.

However, I did go to my dealer, put my ear up to their MC205 and their's hums too.

So is this something natural for an $8000 amp? Any feedback is appreciated.