If you can prove the laptop is quiet on battery the very best solution is to look for a power supply that does not carry mains earth through to the LT side.
Transformer isolators are all very well but can compromise audio quality (and pick up hum) and the usual dodge of dissing signal screens can introduce RFI.
Dave.
Transformer isolators are all very well but can compromise audio quality (and pick up hum) and the usual dodge of dissing signal screens can introduce RFI.
Dave.