Can the NH be left plugged in all the time, or should it be removed after my listening sessions? Also my circuit is 20 amps…
It can be plugged in all the time.
Your 20 amp circuit is not relevant.
Mine NH emits a faint buzz. Does yours?
Noise is NOT normal.
If you can hear it, you should chuck it (IMO).
Sorry for your loss…
I will have to arrange a funeral…