Roberto is absolutely right. I’ve heard his Nait50 at his place and the noise is a serious hum from possibly an internal failure. It hums loudly with no equipment plugged in and it’s not normal. We have checked everything but clearly something went wrong.
@rsch,
Roberto, have the unit sent for repair, period. It’s in full warranty and its behavior is unacceptable. Here you’ll only get suggestions on the lines that you may possibly have missed or ignored some procedure.
Best let the dealer sort it out properly you could bandy words for weeks and not get an answer.
What I’ve missed is if it’s audible hum through the speakers or if it’s a mechanical hum from the box with nothing connected.
Either way if it’s changed with nothing happening then seems like a possible fault.