Mac Mini headphone jack not working 2018

Mac Mini headphone jack not working but I fixed it.

My Mac Mini had been playing music through the headphone jack to speakers for years, when one day I found that plugging in the speakers got silence. Confirmed that the internal Mac Mini speaker gave me sound, confirmed that external cable and external speakers were working.

Checked this "Official Apple Support Community" site, found exact same question. First answer is some "expert" advising (1) Cycle Power, (2) Reset SMC, (3) Reset PRAM and NVRAM. Oh really? Why? There was no suggestion about what the problem might be, just generic "reset everything" advice. That's an "expert?"

Best advice, later on the page, was "check 'Sound' in system preferences." With that clue, I fixed it.

So here are the problem and answer from my experience:

• In System Preferences, went to "Sound" and tab "Output".
• Under "Select a device for sound output" the available value changes depending upon whether or not a headset is plugged in.
  • When nothing is plugged into the jack, the available output device is "internal speaker".
  • When something is plugged into the jack, the available output device is "Headphones".
• Guess what -- there are two separate volume controls, depending upon the device! Absent that knowledge, diagnostics is misleading.
• Hearing sound from the internal speaker does NOT imply plugging into headphone jack should produce sound.
• Do this: Put the plug into the headphone jack. The device listed under System Preferences -> Sound -> Output should now read "Headphones". Check the volume control.
• In my case, volume had somehow gone down to about 10%; as a result I could hear nothing.
• Moved slider to higher value, got sound out of my speakers.
• There is also a "Mute" checkbox; obviously, make sure it is unchecked.

Or, you could take the advice of the "expert" and reset NVRAM and then take it to an Apple Service center. Which-ever seems like a better answer.

By the way, I recently upgraded my OS to High Sierra 10.13.3; not sure if that is related to the lowered volume level.