If you use Winamp (highly recommended), you can reduce the AC (60Hz) hum on some of the feeds by using Winamp's built-in equalizer and rolling off the 60Hz response, as follows:
I am sure other sound players have this capability, but I don't believe any of them make it as easy to get at as Winamp does.
The reason I mention this is that some feeder sites have a difficult time achieving the isolation and/or grounding necessary to reduce the transmitted hum. This technique should be very effective for most listeners.
-dave