Nak AV10 pre-out noise HELP

This is the second time this has happened to me. My brother has a Nakamichi AV10 HT receiver and wanted to add an extra kick for 2 channel so he tried out my Nak PA-7 power amp via his front pre-outs to his front speakers (LaScala’s). The hum was worse than annoying - I changed cables and it still made the same noise. We just called it a bad combination and gave up.

Now, a year later I am trying it on a DIFFERENT Nak AV10 and I'm getting the same problem. The amp ran perfect with my Sunfire TGII when I ran it in my HT system. In fact my friend liked it so much - it lead him to try it out on his system. I'm wondering if there are issues with the unbalanced outputs on the AV10. Nakamichi isn’t much help and Google didn’t get me anything.

I could try a cheater plug ... I will again swap the interconnects but I was wondering if ANYONE out there has successfully ran a AV10 as just an HT processor? Is it possible the pre section of the AV10 just doesn’t run well with that power amp? I would have thought the Nak stuff would match up well. I am considering a test with my Mark Levinson No. 27 but it's raining in the Pacific Northwest and I might not see a clear day for a while. I hate the thought of dragging equipment around this time of year.