Taking into consideration everything you have said so far, then clearly you either have a faulty Beolink Passive or a cable issue.
In my view its more than likely a Powerlink cable issue and the connections for a fully wire cable are below.
The yellow wire connected to pin 4 is the signal which turns the Beolink Passive on (green Led). There are some units I have come across which have pins 1 and pin 4 reversed which allows the unit to power up, but gives a loud noise when switched off.
If the cable you are using is a standard B&O cable then it should be fine otherwise I suggest you check teh connections.