I did experience the stuff described below, so I stopped using this card in linux. Cirrus Logic (the DSP maker) suck badly at disclosing info on this years old chip, so there's not much hope at this getting better. Just forget about it.
From alsa-project.org:
Santa Cruz cs46xx driver:
There is a known problem with random metallic distortion during recording and playback:
(SEE:
http://www.mail-archive.com/alsa-dev.../msg09687.html)
Antidotal Fixes:
Recording: Open alsamixer and toggle Capture on and off with the [space bar].
Playback: Open alsamixer and toggle ADC and DAC levels ([0] for off,
[PgUp] for incremental increases)
Playback: Open alsamixer and togge External on and off with [M].
XMMS/General: stop and start playback (not pause) OR close and reopen application.
Last Option: reload modules
1) Close or kill all applications using sound (e.g. XMMS, aRts, volume controls).
2) # modprobe -r cs46xx
3) # modprobe cs46xx
(snd-cs46xx may be the correct name, esp. in 2.4.x kernels.)
(Debian users may use # /etc/init.d/alsa force-reload)
(NOTE: Monolithic kernels will require a computer reboot.)