So I recently got an analog 5.1 (3 separate plugs) surround speaker system, and plugged it into my onboard Realtek. The audio keeps randomly cutting out. Like I can't listen to a 3 minute song without getting half a dozen 4-second interruptions, where the music keeps playing, but nothing comes out of my speakers.
I tried a different set of speakers, just to make sure it wasn't my speakers, and it still happens. It only seems to happen if I select quadraphonic, 5.1 or 7.1 audio output - it works fine on stereo. On the "communications" tab of the sound properties dialog, I have it set to "do nothing", not "mute all other sounds" when windows detects communications activity, so that's not it.
It doesn't seem to matter what the volume of the source audio is, whether it is quiet dialogue or loud explosions, the audio can cut out at any moment for any reason.