A problem I get only since getting windows 8.1 – The speakers stop working a few hours into a session. The work again after a reboot.
The headphones work when the speakers stop working.
In the sound settings box, playback tab, the Digital Audio (S/PDIF) level goes up and down but nothing in the speakers volume level. Many applications like itunes wont start to playback tracks, realising there is a problem. Rather than just playing with no sound being heard. Plays fine with headphones inserted.
No idea what is going on but I dont want to wait for 8.2 or reboot every few hours
Update>
If I make a call on google hangouts, from within gmail , and the call fails – then there is a high chance the sound will stop, but work for headphones. I dont see the sound fail in any other occurrence.
Best Answer
Had a similar problem back in the 90's with my line-in jack... turned out the jack was overheating due to bad airflow. rebooting gave it (and the video-card above it) a minute or so to cool down.