Thank you for the answer, George.
Most or all of the confirmations about the Summit X noise are from Europe.
I was sure that every Summit maybe the the Montis too, produce this noise.
In my home it is very very quiet and i use the Summit not to far from my hearing position, almost near field.
Thats why i recognized the noise, which is really quiet indeed.
To my surprise a lot of the users could not hear that, and most of them on a different power system than the German one.
So the possibility of an European, power system related error, was there.
But you are absolutely right, the Summit X is a wonderful sounding Loudspeaker and for my personal taste one of the best i ever heard.
Cheers
Karl