>Maybe I misunderstood - I thought that, by "sound system", you meant a stereo/hi-fi system with a receiver or amplifier. If the receiver or amp are near a running computer, microwave oven etc. there might be interference that could cause background noise.
>
>For getting sound into the sound system I'd first try hooking a cable from the laptop headphone output into an "AUX" connector on your receiver/amp.

Wow, you were right. There was some interference. It was the power cable of the laptop. I plugged it initially in a new set of wall plugs, such as 5 in a row all in the same breaker. When it was there, it was causing the interference. When I tried a separated plug in the wall about 10 feet from there, the problem went away.

Thanks