You may find having some test files useful. Here is what I use (specifically, the mp4 version…the sound is amazing):
If you install something like mplayer or xine, naming this file as an argument should play correctly for the number of channels you have (I’m using 7.1 Surround Sound headphones).
I find all audio sometimes frustrating, as mixer settings are often just a jumble of devices and parameters with absolutely no intuitive naming…a LOT of trial (and mostly) error to get it right. I find that often any app which has a pulse-audio front end tends to set things up for me, whether I use that program or not. One of my first audio tests on the JTX1 was to install the “mumble” voice chat software and make sure it could see and use both USB headset speakers and microphone. Once I do this, other things typically work. This also means that although you won’t necessarily know why one part of audio setup in the mixer has a given setting or not, you can now dump the audio mixer settings and use that for a baseline in future audio setup.
Does this file play correct with any of your video apps?