I recently switched to Mavericks and now I've lost all audio out for my MacBook Pro. I've followed regular system preference checks, and no fix. Please advise. Thanks.

Things to check

go to system preferences.sound/ output see if you can select built in speakers, make sure the volume is up mute box is not checked

try plugging a set of headphones in and out several times (there is a micro switch that sometimes gets stuck)

go to applications/utilities/Audio MIDI set up output tan select built in there in the left, make volume is up and mute is not checked

Try a NVRAM/PRAM reset:

Power off, power back on holding COMMAND OPTION P R continue to hold these keys till you hear the start chime 2 times then release, reboot.