Beolab 12 buzzing noise

Hello, as I am expanding my surround sound set up I have added some Beolab 12 as surround speakers. Front speakers are BL5 and BL10 with Beosystem 4 as processor. After adding the BL12 I immediately noticed a buzzing noise. When the Beolab 12 turn on they make an electronic signal noise like 3 beeps. They play music but with a constant humm in the background. Beosystem 4 is linked to right surround speaker and then daisy chained from right to left surround speaker. The strange thing: I tested left surround together with left front as stereo set up and everything plays fine without buzzing. The same when I play right surround and right front as a stereo set… When I play 5.0 the surround speakers buzz, not the fronts. Any ideas, could it be the 15m powerlink which goes under the floor for about 6m in total towards right surround? Or perhaps the cable jungle around the Beosystem 4 with these radio frequency cables to the Apple TVs (these sometimes interfere with my screen). Any suggestions are welcome, thank you, Paul

Sounds like a grounding issue to me, either the cable isn’t fully seated or there is a possible break in the shielding somewhere. Most obvious is that the cable is seated but just lack that last bit of good contact. I’ve had the same before too

Mikipidia, I believe you are right. It is possible that the cable got damaged during installation in the wall. I will buy a new powerlink and try it out. Thank you