10.10.4 Build 14E33b --- lost sound in/out

[Fishrrman]

Hello all -

I've been running Yosemite from an external firewire 800 drive, connected to a late-2012 Mac Mini.

Up through and including public beta Build 14E26a, everything has been fine.

BUT --
After installing the just-released public beta Build 14E33b, I have lost sound in/out.

The Mac still -has- sound.
It still plays the startup sound, so I know the speaker is good, the connection to the motherboard is good, etc.

If I open System Information and click on "Audio", it shows all the normal connections:
- Intel High Definition Audio
-Headphone
-Speaker
-Line Input
-S/PDIF Optical Digital Audio Input
-S/PDIF Optical Digital Audio Output
All of the above "appears at it should be". The computer (at least down at the hardware level) knows these connections are there, or are at least "possible".

The essential .kext file is in place in the extensions folder:
AppleHDA.kext

But somehow the kext isn't loading, or is corrupt, or something else, because it does not seem to be "establishing" the normal audio connections that would be established at boot time as the kexts "load up".

I will admit that my knowledge regarding the handling of kexts is limited.

Has anyone else seen this problem?
Can anyone point in the general direction of a solution?

 

[Fishrrman]

A followup to my original post.

I spent the better part of two days trying to overcome this problem.

I finally got it resolved by:
1. Installing a fresh copy of 10.10.0 onto an empty partition
2. Migrating all my data/apps/accounts from the existing Yosemite boot partition
3. Downloading the 10.10.4 latest beta preview and applying it directly against 10.10.0.

Even with some bumps along the pathway above, it finally got me back to where I had a working copy of the latest 10.10.4 beta with sound once again enabled...