Chosen Solution
The system audio device of my Mac Mini 2012 isn’t available, neither in System Preferences nor in the System Report. I bought this Mac Mini only recently second hand, replaced the second hard drive with an SSD, and made a clean install install of OS X 10.11. I hardly used the computer before and therefore can’t say for sure if the system audio device had been working before. Any clues what could be the cause, and how to fix it? Audio output over DisplayPort/HDMI works. SMC and PRAM reset did not solve this issue. Update (11/11/2021) @danj Thanks again for your help. I had another look at the logic board but found no suspicious traces near the audio chip - at least no difference to other areas. Maybe you can see something? I think I’ll leave it as it is now before I cause any serious damage to the Mac’s innards - unless of course you or someone else have further suggestions.
Ah! A Where’s Waldo problem! First do you hear the Bong startup sound? If you do that tells us the logic board DAC is working Second look at your System Preferences > Sound do you see in the Output section the two listed outputs: Analog and Digital Out? If you only see Digital then that’s telling us the headphone jack has a problem. Try plugging in a headphone do you hear your music or other audio? Putting it in and out may fix things. Sometimes the little blade switched inside get messed up and need a little work to fix either because they shifted or they are dirty
Sadly you can’t replace it as its mounted directly on the logic board. You may just need to use a set of speakers.
