Plugging in External Monitor disables audio?

[victorhooi]

I'm running OSX 10.11.1 (15B42) on a 2015 rMBP 13".

I have a Dell P2715Q monitor - I'm connecting this via a DisplayPort to Mini-DisplayPort cable to one of the Thunderbolt ports on the Macbook.

My sound works fine normally.

However, as soon as I plug in the monitor, OSX seems to disable the sound.

If I try to adjust the volume, this is what I see:

And of course, sound doesn't work in any apps (Chrome, Skype etc.).

Any thoughts on what's going on, or how to fix it?

Or how I can gather more diagnostics on what's happening? Could this be an OSX bug?

 

[Autistic Behaviour]

you can choose which audio output to use by clicking the option key while clicking the sound icon in menubar

 

[victorhooi]

Aha, you're right - I just noticed that it defaulted to trying to push sound via the DisplayPort as well.

The monitor has a 3.5mm audio out - so I'm guessing it's trying to go rMBP -> DP to Monitor -> 3.5mm out. Not sure it's the best default, but oh well =).