amixer set "Master" on 100%
amixer set "PCM" on 100%
At this point, speakers plugged into the green jack in the rear of the
machine should work.
Headphones (the jack in the front) can be controlled with the
Headphone
device:
amixer set "Headphone" on 100%
Volume can be controlled by the percentage specified:
amixer set "Headphone" on 50%
(100% can be a little loud on headphones.)
To enable the microphone jack in the front:
amixer set "Mic" cap