Great help from tech support (Steve and Scott) today. Suggestion was made to troubleshoot, thinking of possible ground loop. So at outlaw suggestion I temporarily "lifted" the ground by inserting a "cheater". Hum went away. Dead quiet.
Now I know that I don't want to delete the ground pin, nor does outlaw want us to eliminate the safety accruing from ground. This was just a test, but what a simple test to do.

So it proved what I thought all along, that the amp was OK. After that I changed some things around. No hum. Dead quiet. Will check it again in AM after it has had a good snooze tonite. I expect it will be fine.

I still don't know why I had hum (ground loop) but as usual I'm quite happy with the product, the service, and support.

My $.02