McIntosh SS Owners Question

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.