Quote Originally Posted by bumpy View Post
I'm struggling too. If you put a resistor between the ground of the cable and a case that is not connected to earth, then its seems no better than inserting a resistor and dangling the other end in fresh air.
I agree, I think Ali is suggesting that the resistor is inserted in the 'ground' connection out to the output sockets.

As far as an earth lift goes in an earthed case system, the extra resistance between the signal ground loop and the earth loop forces any current that is flowing to flow in the earth connections between cases, rather than the signal connections, thus reducing the 50Hz currents to virtually zero.