"Dave Plowman (News)" wrote:

Eiron wrote:
Earth loops occur when there are two ground paths at different
potentials. Usually the screen of the interconnecting cable and mains
earths via the mains plug. And takes the form of hum. If you are
running the laptop on batteries with the power supply disconnected
totally it can't be an earth loop.

Could the problem be that there is no earth in the system
rather than too many?

If there's no ground connection between the two using unbalanced
connection you'll not get any signal either.

The problem is that almost no-one here realises what's inside an SMPS ! AND
probably wouldn't believe it if they knew.

Graham