The NAD T163 produce a almost inaudible hum noise when either using the analog inputs, or when the setting is Stereo. When using digital inputs or a surround processing (EARS, MATRIX, DTS, DPLII, etc) I cant hear nothing, even pumping it to +15dB.

I am troublehsooting that noise with the NAD dealer, now that I am getting the upgrade done. I will let you know what we found.

BTW, getting the upgrade is what have kept me from posting the EP500 resolution. The new sub arrived but I have not use it yet. But I plug it and I can see that the "thump" noise that the old one had when shutting it down is gone, so high hopes for this one (I did not mention this noise in my first post, I discussed it directly with Brent Tombari at Axiom, as I was not sure of the integrity of the sub since it arrived)

The upgrade is not available inmediately. The dealer told me that they need the D-Tools software and the upgrade files. Some dealers in Houston area told me that it will take 2 weeks to get the upgrade, but my dealer in Austin was already working on getting it, so I expect less than a week. (I might travel overseas the next week, so please wait a couple of weeks before the EP500 is tested again)