But now to the actual reason for my review:
I also had a problem with the noise or hum described already often here, I have garment to Logitech's support and described the problem.
Lo and behold, there is a new, improved version of the Z506 - so I did everything clear for a replacement, which went smoothly!
Today the package came. First I noticed the box - a new design.
My guess is that a new power supply has been installed! Otherwise, there are no external changes.
But the most important thing -> The noise is gone !!!!!!!! * Yay *
Can only advise everyone to exchange at Logitech ...