While my TT was humming one channel, leaving the interconnects hooked up but unplugging the TT from the wall made it go away. Replacing the TT's worn RCA females didn't help. Renewing the interconnects did.
Since you've got hum on any source it sounds like the amp is the misbehaver. Maybe your amp was in storage/left unpowered for a long time?
I stowed an OK-fine SS Dynaco 120 power amp in a hot Dallas attic. A couple of years later, it powered up and still worked but the transformer hummed in the chassis. Tightening the hold down bolts didn't help. That amp had failed two times prior (over one 8 cent and one 15 cent part respectively), so my solution was to sell it at half its value to someone who was willing to isolate the hum's exact cause. Sorry it's not much help. How attached are you to the NAD?
Since you've got hum on any source it sounds like the amp is the misbehaver. Maybe your amp was in storage/left unpowered for a long time?
I stowed an OK-fine SS Dynaco 120 power amp in a hot Dallas attic. A couple of years later, it powered up and still worked but the transformer hummed in the chassis. Tightening the hold down bolts didn't help. That amp had failed two times prior (over one 8 cent and one 15 cent part respectively), so my solution was to sell it at half its value to someone who was willing to isolate the hum's exact cause. Sorry it's not much help. How attached are you to the NAD?