Bizarre noise issue

[MarcAshken]

i have exactly the same problem with my laptop when its plugged in, I bought a stereo DI box from turnkey, cost me about £20, has an option to lift and ground totally eliminating hum. Its a ballache draggin it round all the time but it sorts the problem out.

[kujoma]

many laptops are noisy when the PSU is plugged, and become silent when operating on batteries...

I have this problem too, unpluging the power supply should solve the problem.

[steevio]

i shouldnt be telling you to do this, but if you want to sort it instantly, - with everything switched off, disconnect the earth lead from your laptop's power supply lead's plug. (and tape it up out of the way )
as long as your soundcard is connected to the mixer and the mixer is earthed, then you are safe. (its what an earth lifter is doing anyway)
i have to do this at every gig, its a really common problem. (ive got a little screwdriver taped to my power lead so i dont forget)
but when you can get hold of a proper device, get one for peace of mind.

[Measax]

its caused by a ground loop...I guess it depends on the country your in...I had this problem with every pc I ever owned...never had the issue with a mac laptop (guess that speaks for the quality of apple products).

[skept]

nm