noise from laptop psu on audio out

[Mark Hennessy]

It might not be an earth loop as such (although being a SMPSU doesn't rule that out by any means), but SMPSUs can have high leakage currents between input and output, so if the laptop chassis isn't connected to earth via the PSU, this could be a factor. Otherwise, try an external USB soundcard, as I mentioned previously, because many laptops suffer this problem and there is no cure short of redesigning the motherboard...

Good luck,

Mark