You may already have the answer, but I just received mine (thanks to a deal published by @VintageFlanker :D) and can confirm the LED can be disabled both when listening to music/source and when sleeping.
I am indeed a first time poster as mostly a lurker/reader of reviews and waiting for an opportunity on an ncore amp in Europe for a while.
Is there a restriction about it?
BTW, no sale yet as the seller didn't answer to my request to go PM.