A very strange thing just occurred with my MacBook Pro. The audio output stopped completely, it was working earlier today. I tried to change the volume, and it showed as muted but with full volume, a bit weird. Plus it started emitting a strange red light out of the headphone jack.
A little searching and supposedly the headphone jack does optical audio out, which some how must of got turned on. Considering all I use the headphone jack for is headphones, I’m not sure how that happened.
After a little more searching, configuration changes and attempts to restore audio output, I just ended up plugging in my headphones hoping it will some how reverse it’s current state. And it worked. Go figure.