Re: sound card problems
Francesco, with most video / audio players you can configure which sound source shall be used (in their preferences).
Install alsamixergui, the most simple tool. If you don't know what those channels refer to, turn up anything then turn down those which don't make a difference. (Click the lock to sync left/right)
btw. Just this morning i deinstalled pulseaudio from two fresh installed Debain 'testing' PC and then it worked. I never understand why, for Desktop usage, anything beyond alsa itself should be necessary. While there's of course quite a lot for more professional users, but that should be optionally, shouldn't it. KDE uses phonon, at least it seems to work out of the box.