McIntosh SS Owners Question

I have a McIntosh MC206 amp. When I turn it on I hear a very low hum. With any volumne at all you cannot hear the hum. Should this amp when turned on by itself be 100% quiet?
Your MC206 should be dead silent, no hum. Is this a 60hz line hum by chance? If so check you AC line. Also make sure there are no dimmers on the same line.

They are excellent amps. I hope all goes well keep us posted.

Agreed. There should be no hum at all. Have it checked out.
I had a MC7205 which is the same chassis as the 206 Sans 1 channel. I had the same hum and determined that it was the power supply resonating through the shelf. I found some ModSquad rubber feet that eliminated the hum. Those are no longer made but a similar foot such as sorbathane etc may be your solution as well.
I unplug my Power Conditioner and plugged it into a different outlet. Hum gone.
Was the hum coming from the speakers or the amp itself? If the former, you probably have a ground loop issue.

Lots of discussion here on AG if you enter "ground loop" in the search field.
That reminds me I used a PS Audio PC with the ground plug removed. Sorry I had forgotten to mention that, old age memory lapse.
from the amp
Yes amp to power conditioner I was minus the ground plug.