Jack

Steps to getting jack to run

Disable pulseaudio

a less drastic measure http://jackaudio.org/pulseaudio_and_jack

Remove pulseaudio

Pulseaudio, like Jack is a sound server, and the two don't co-exist very well, so we might want to remove it

from: http://crunchbang.org/forums/viewtopic.php?id=23930

sudo killall pulseaudio
sudo apt-get purge pulseaudio pulseaudio-utils gstreamer0.10-pulseaudio libpulse-browse0 paman pavumeter pavucontrol
sudo mv /etc/asound.conf /etc/asound.conf-bak
rm ~/.pulse-cookie
rm -r ~/.pulse

Reboot

Install required alsa tools

sudo apt-get install alsa-base alsa-tools alsa-tools-gui alsa-utils alsa-oss alsamixergui libalsaplayer0

Test Alsa

mplayer someaudiofile.mp3

While the file is playing, and specially if you aren't hearing any sound, open the alsamixer

alsamixer

and check if the output volume (Master, PCM) is up and if the channels are not muted (MM on the bottom mutes. If sound select the channel and unmute w/ 'm' key)

if mplayer doesn't seem to be playing, then maybe it is because you - the user - are not in the audio group

sudo adduser yourname audio

Reboot and try again to play something through mplayer

Start Jack

the easy way is to use qjackctrl to start and manage jack connections

qjackctrl

start jack (Play button) in qjackctl

if jack starts without problems, you can test jack by using mplayer with jack as audio output ( -ao jack )

mplayer someaudiofile.mp3 -ao jack

sound or no sound?