OS X El Capitan no sound output device found Every time I start my Mac, there's no output device listed in system preferences > audio. In order to fix this, I have to reset SMC several times. I also tried to reset NVRAM. However, if I turn off the Mac and start it again the next day, the same problem appears again.
This problem first occurred, after I installed soundflower. But I uninstalled it already.
I'm using Mac Mini late 2012 with common Logitech loudspeakers. 




When I run Apple Hardware test, it outputs this result:
4hdd/11/40000000: Sata(0,0)
The very first thing I would do is run an Apple Hardware Test.

When you turn on the computer, before you hear the startup chime, press and hold the D key.

Also, there is one item to double check and that is if you uninstalled Soundflower completely.

Use an app like  AppCleaner to ensure that you've got everything associated with the app.  Best of all, it's free.