Hum on A.C. power, not ground loop.

[gyppo]

I've had an annoying hum produced through the headphone socket whenever I've had the A.C. power plugged in. It varies with the brightness of the LCD screen, getting louder when I move the mouse and quieter when the screensaver comes on.
My initial thought was that this was a ground loop caused by a faulty earth, or the speakers I've plugged in having a different D.C. offset from the laptop, or something similar. But when I booted MS Vista on the same machine with the same setup no buzz could be heard. To reiterate, sound coming through the built-in speakers is fine, it's only when I plug something into the headphone socket while plugged into the mains.
Can someone help me please? It's driving me nuts!

[jerrrys]

just an idea

you have three different sound options. Pulse; OSS; ALSA

[Whiffle]

I've had an annoying hum produced through the headphone socket whenever I've had the A.C. power plugged in. It varies with the brightness of the LCD screen, getting louder when I move the mouse and quieter when the screensaver comes on.
My initial thought was that this was a ground loop caused by a faulty earth, or the speakers I've plugged in having a different D.C. offset from the laptop, or something similar. But when I booted MS Vista on the same machine with the same setup no buzz could be heard. To reiterate, sound coming through the built-in speakers is fine, it's only when I plug something into the headphone socket while plugged into the mains.
Can someone help me please? It's driving me nuts!

Try opening up the mixer and muting different channels, it sounds like you may have a line in or something that isn't connected to anything, but isn't muted either, so its picking up interference and channeling it into your speakers.