The optimum configuration for each system is one Ground/Earth for the whole system. If a system has multiple Grounds/Earths, then it often creates unwanted ground loops. These systems will then have an annoying low-frequency hum (emitted from the speakers).
Current solutions either jeopardise (i) both safety and EMI shielding (e.g. cheater plug), or (ii) EMI shielding. And most are single country (US) uses only.
The GND Defender in the correct way, intelligently detects a ground loop and will cut the ground for that component.