Don't mess around with JACK when you don't yet have ALSA working. Like
Pulseaudio, JACK is a sound server that controls and relies on ALSA.
Pulseaudio is intended to work out-of-the box for basic desktop usage. JACK
is more advanced (i.e. for professional audio production) and requires more
configuration. I know a lot of musicians, so I frequently set up JACK on
people's laptops, and every new sound card I encounter is a unique
pain-in-the-adventure. Installing JACK has the potential to break sound if it
was already working, but if ALSA already wasn't working then JACK won't make
things any better. If you're a musician, I'll help you through installing and
configuring JACK *after* we get ALSA working. Otherwise you're better off
with ALSA+Pulseaudio or (if you don't use GNOME or a Firefox-based browser)
just ALSA.
I've seen many cases where these things worked with just ALSA but not with
JACK+ALSA. Pulseaudio+ALSA has worked on the dozen or so laptops on which
I've install Trisquel 8, but I have heard of people having problems with it.
For now lets keep it simple and just get ALSA working.
Purge ALSA, Pulseaudio, and JACK. Reinstall *just* ALSA. Run "alsamixer" and
try all of the available devices. Don't test audio through Abrowser, because
Firefox-derivatives no longer work without Pulseaudio. Instead play an audio
or video file through your preferred media player.
