Sound issues (poor quality) since upgrade to 11.10

[kln]

I have been experiencing very poor quality sound (noise, saturation, etc.) since the upgrade to Oneiric. Some days, it also happened that I couldn't play sounds at all, but later it came back.

As soon as I select Phonon in System Settings > Multimedia, I get a notification asking me if I want to forget about HDA devices. I then only find available the Internal Audio Analog Stereo choice.

Here is the message :

KDE detected that one or more internal devices were removed.
Do you want KDE to permanently forget about these devices?
This is the list of devices KDE thinks can be removed:
Capture: 
Capture: HDA Intel (ALC262 Analog)
Output: 
Output: HDA Intel (ALC262 Analog)
Output: HDA Intel (ALC262 Digital) #3
Output: HDA Intel, ALC262 Analog (Direct hardware device without any conversions)
Output: HDA Intel, ALC262 Analog (Direct sample mixing device)
Output: HDA Intel, ALC262 Analog (Hardware device with all software conversions)

I reinstalled pulseaudio, and tried also $rm -rvf ~/.pulse/, to no avail.

About the system :

$ cat /proc/asound/card0/codec* | grep Codec
Codec: Realtek ALC262

$ lspci -v | grep -A7 -i "audio"
00:1b.0 Audio device: Intel Corporation 82801I (ICH9 Family) HD Audio Controller (rev 03)
    Subsystem: Device 1a46:1405
    Flags: bus master, fast devsel, latency 0, IRQ 46
    Memory at db300000 (64-bit, non-prefetchable) [size=16K]
    Capabilities: <access denied>
    Kernel driver in use: HDA Intel
    Kernel modules: snd-hda-intel

$ cat /proc/asound/cards
 0 [Intel     ]: HDA-Intel - HDA Intel
           HDA Intel at 0xdb300000 irq 46
 1 [Camera     ]: USB-Audio - Sirius USB2.0 Camera
           Vimicro Corp. Sirius USB2.0 Camera at usb-0000:00:1a.7-3, high speed

$ dmesg | grep -i alsa
returns nothing 

$ sudo aplay -l
**** List of PLAYBACK Hardware Devices ****
Home directory /home/xxx not ours.
card 0: Intel [HDA Intel], device 0: ALC262 Analog [ALC262 Analog]
 Subdevices: 0/1
 Subdevice #0: subdevice #0
card 0: Intel [HDA Intel], device 3: ALC262 Digital [ALC262 Digital]
 Subdevices: 1/1
 Subdevice #0: subdevice #0

I tried to add "options snd-hda-intel model=zepto position_fix=1" at the end of alsa-base.conf (and rebooted), since my laptop is a zepto, but that didn't make any difference. Also tried with "options snd-hda-intel probe_mask=1 model=auto", no success.
Should I try all the ALC262 options in HD-audio-models.txt one after the other, or is there something else to diagnose ?

[kln]

Re: Sound issues (poor quality) since upgrade to 11.10

Additional console output

$ lsmod | grep -i "snd"
snd_hrtimer      12744 1 
snd_hda_codec_realtek  330769 1 
snd_usb_audio     118064 1 
snd_usbmidi_lib    25371 1 snd_usb_audio
snd_hda_intel     33390 2 
snd_hda_codec     104802 2 snd_hda_codec_realtek,snd_hda_intel
snd_hwdep       13668 2 snd_usb_audio,snd_hda_codec
snd_pcm        96714 3 snd_usb_audio,snd_hda_intel,snd_hda_codec
snd_seq_midi      13324 0 
snd_rawmidi      30547 2 snd_usbmidi_lib,snd_seq_midi
snd_seq_midi_event   14899 1 snd_seq_midi
snd_seq        61896 3 snd_seq_midi,snd_seq_midi_event
snd_timer       29991 3 snd_hrtimer,snd_pcm,snd_seq
snd_seq_device     14540 3 snd_seq_midi,snd_rawmidi,snd_seq
snd          68266 18 snd_hda_codec_realtek,snd_usb_audio,snd_usbmidi_lib,snd_hda_intel,snd_hda_codec,snd_hwdep,snd_pcm,snd_rawmidi,snd_seq,snd_timer,snd_seq_device
soundcore       12680 1 snd
snd_page_alloc     18529 2 snd_hda_intel,snd_pcm