We have had customers that have inadvertently connected a speaker to the unit while it is live and I assume one of the speaker cables has touched the metal case (earthed) and caused the TDA7498 to fail.We have also had technicians connect oscilloscop...
Apologies misunderstood what you said.Yes the power supply has an AC transformer providing isolation.We do however connect circuit ground to chassis ground via a 10 Ohm resistor, see schematic.