Ok, I just opened the case and saw no SoundBlaster card (I wrongly assumed that all PowerMac MDD had one)... So I only have the onboard sound chip, hence the AppleI2S driver... Still, the sound is very low, so it doesn't work well (the chime sound works perfectly good and is very loud ;) ).
So what should I do? Is there a way to fix the sound anyway, or should i buy a Soundblaster Live! ?
"A good bug is a dead bug" (Don Dailey)