philcud said:

lastly, if i 'half' remove the power lead from the laptop, such that
the laptop tells me that it is not receiving any power from the lead,
but the lead is still halfway in the socket (maybe earthing?) there is
no distortion to the signal whatsover.

the laptop is an old audiolab powered by a 'kettle' type lead (3
prong).

On the 3 pin IEC plug/socket for safety reasons the earth pin is
longer than the live/neutral so the earth connection is first to
make and last to break for safety reasons.

Are both the lap top and amp plugged into the same ring main or wall
socket?

Is your amplifier earthed?

If it is, have you tried disconnecting the earth?

What happens if you leave the power lead plugged into the laptop and
switch the wall socket off so that the laptop is not connected to
power but is connected to earth?

Have you tried disconnecting the earth on the laptop power lead or is
it a moulded plug?
Which you could cut off and replace with an ordinary plug if you want
to try that.




--
Ken