After much delay, I finally got my problem resolved.....and quite nicely!
Doug Dale, the owner of Coda, had been severely injured many months ago and has been off work until last week. Much of the delay that I experienced was due to Doug's absence. He was apologetic for the delay.
As soon as he got back to work, he decided to simply swap out my unit for a new one that he had tested and was sure worked to spec....with no noise. I brought my amp in today. We listened to it in his listening room and (thankfully) heard the noise....although it was MUCH quieter in his room with his Legacy speakers that it was in my room with my speakers. We then listened to the new amp that he had selected to replace mine.....it wasn't dead quiet, but the noise was of a much less obtrusive nature that he said was normal and (I believe) related to the volume control used.
I brought the amp back to my house, plugged it in and......it's lovely...no noise. Again, not dead quiet, but WAY more quiet than my previous unit. Since the replacement unit is new I'll have to break it in again, but, frankly, that's not that bad a prospect :-)
Doug did say that very infrequently, generally due to shipping issues (dropping, rough treatment) some wires get slightly loose and may cause the issue I have been having. Oh well, just bad luck on my part.
It was cool seeing the Coda facility.....there's only 4 employees (that I saw) including Doug, so it's a small operation. But they're producing some neat products.
OK, I'll check back in in a few weeks....but I'm VERY heartened with today's news. Thanks again to all of you for your support and help.