It's an original CB1 that was upgrade at theta around 4 years ago to CB3.
Until today I have worked at 5.1 (didn’t use the side spk)
During the last week I have added side's spk and from time to time I here a very strange sound from one of the side spk (like old vinyl record that is very scratched).
Only when I disconnect the cb3 from the outlet power cable and returns it again the problem disappear but returns after 2-3 days
Any help will be much appreciated