Compaq Presario 731US Soundcard: ADI/SoundMax

Hi,

I'm having trouble getting my soundcard working in FreeBSD 4.6.2.  It is detected correctly on bootup:

pcm0: <VIA VT82C686A> port 0x1850-0x1853,0x1854-0x1857,0x1000-0x10ff irq 5 at device 7.5 on pci0

However when I try to play an mp3 in xmms it plays but no sound is produced.  I tried mixer `mixer -s`, but that didn't help either. The volume is at 100%.  I also attempted to use cat somefile.wav > /dev/dsp, there is a pause about the length of the file and then it goes back to the prompt.  Here is what pciconf -lv reads:

pcm0@pci0:7:5: class=0x040100 card=0x00970e11 chip=0x30581106 rev=0x50 hdr=0x00 
vendor = 'VIA Technologies Inc' 
device = 'VT82C686/A/B AC'97 Audio Codec' 
class = multimedia 
subclass = audio

It seems the sound is muted or something, but the mixer does not report this.  I tried different volume levels, but cannot hear anything.

Thank you for any help,
Dominik