This is because ALL power supplies for desktop pc's are tested in an environment where there is only ONE source of power. Laptop power supplies are tested also independantly and most likely never tested in an environment where the connection between the AC ground and the DC ground is checked out. THIS IS WHERE THE PROBLEM LIES. If the design of the internal battery power supply and the external ac power supply is not implemented correctly there is a connection, and it shows up dramatically in a situation where there is a noisy ground on the AC side which is easily detected on the audio where the audio ground is improperly connected to the ac ground. It is a similar problem in Marine applications, where there is a shore power system, an on board generator system AND a Dc system . If everything is not correctly set up you can have similar problem but they are reflected in significant corrosive deterioration of underwater metals.
SO IMO when you have this laptop situation basically the only truly safe operational status is when it is on Battery supply ONLY. If you lift the ac ground on the powersupply you run the risk of a Power supply failure becoming dangerous, IF on the other hand you DO NOT lift the ground and there is a serious ground fault on the AC supply, then the laptop also becomes dangerous. The reason why switching power supplies might not resolve the problem is when the problem is in the internal connection between the battery power, ac power supply and the pc audio system
Sharyn
SO IMO when you have this laptop situation basically the only truly safe operational status is when it is on Battery supply ONLY. If you lift the ac ground on the powersupply you run the risk of a Power supply failure becoming dangerous, IF on the other hand you DO NOT lift the ground and there is a serious ground fault on the AC supply, then the laptop also becomes dangerous. The reason why switching power supplies might not resolve the problem is when the problem is in the internal connection between the battery power, ac power supply and the pc audio system
Sharyn
