I've been having some slight troubles with my onboard sound chip, an Intel ICH6 family chip. This is the output from 'lspci -v':
0000:00:1e.2 Multimedia audio controller: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family) AC'97 Audio Controller (rev 04)
Subsystem: Acer Incorporated [ALI]: Unknown device 006a
Flags: bus master, medium devsel, latency 0, IRQ 10
I/O ports at 1c00 [size=256]
I/O ports at 1880 [size=64]
Memory at 80000800 (32-bit, non-prefetchable) [size=512]
Memory at 80000400 (32-bit, non-prefetchable) [size=256]
Capabilities:  Power Management version 2
I'm currently using the kernel snd-intel8x0 driver, and there's a small amount of distortion. This is especially noticeable in low bass, high volume, or a combination of both. Sometimes it even happens with no special circumstances at all. Testing this same chip under Windows (dual-boot), there is no distortion at all, whatsoever (well, that I can hear at least).
The laptop I am using this on is an Acer TravelMate C310, and I'm running Gentoo with a 2.6.11 kernel and ALSA version 1.0.9.
Thanks in advance and cheers!