hd audio problem

Hi !
I'm trying to get rid of my sound card lags (snd_hda driver). The 
problem is:  the sound is often stopping for a small amount of time. I'm 
not having high load average, about 0.5 - 0.8.
I've tried playing with sysctl knobs. Current values are :

sysctl -a | grep snd

hw.snd.report_soft_formats: 1
hw.snd.latency: 8
hw.snd.latency_profile: 1
hw.snd.feeder_buffersize: 65535
hw.snd.feeder_rate_min: 1
hw.snd.feeder_rate_max: 2016000
hw.snd.feeder_rate_round: 25
hw.snd.verbose: 1
hw.snd.default_unit: 0
hw.snd.maxautovchans: 8

my hardware from dmesg :

dmesg | grep pcm
pcm0: <NVidia MCP51 High Definition Audio Controller> mem 
0xfe024000-0xfe027fff irq 21 at device 16.1 on pci0
pcm0: <HDA Codec: Analog Device AD1986A>
pcm0: <HDA Driver Revision: 20070128_0039>

uname -a
FreeBSD doer.home.net 7.0-CURRENT FreeBSD 7.0-CURRENT #1: Tue Feb 20 
17:01:35 UTC 2007     root_at_doer.home.net:/usr/obj/usr/src/sys/DOER  i386