Audio Not working After Debian Upgrade (Lenny, Squeeze & Sid)

I've upgraded many of the packages on my system using Synaptic, which upgraded various components including the kernel and KDE4. As a result I now no longer have audio.

uname -a gives me:

Linux alchemist 2.6.32-trunk-amd64 #1 SMP Sun Jan 10 22:40:40 UTC 2010 x86_64 GNU/Linux

lspci -vv gives me:

00:1b.0 Audio device: Intel Corporation 82801H (ICH8 Family) HD Audio Controller (rev 04)
    Subsystem: Acer Incorporated [ALI] Device 011e
    Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
    Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
    Latency: 0
    Interrupt: pin A routed to IRQ 22
    Region 0: Memory at 98400000 (64-bit, non-prefetchable) [size=16K]
    Capabilities: <access denied>
    Kernel driver in use: HDA Intel

KDE is on version 4.4.3

I don't have PulseAudio installed.

Alsa is on version 1.0.21

Using KDE's Settings tool for audio I've tried both the Xine and GStreamer backends, which give me options of outputting to either HDA Intel (ALC268) or to Jack. Neither option works.

Running alsactl init both as root and as the normal user gives me the following error:

Unknown hardware: "HDA-Intel" "Realtek ALC268" "HDA:10ec0268,1025011e,00100003  HDA:14f12c06,1025011e,00100000" "0x1025" "0x011e"
Hardware is initialized using a guess method

I'm fairly experienced as a Linux user, but I haven't had to reconfigure my sound since I moved from Slackware to Ubuntu 6 04, 4 years ago, and I don't think I've done a kernel recompile since then either.

The machine in question is my Acer Aspire 5720 Laptop. sound was working perfectly prior to the upgrade, Google has given me various ideas but none of them have worked yet.

EDIT I've tried the following:

• Switching between the different backends.

• I've also tried adding the line "options snd-hda-intel index=0 model=72" to the bottom of alsa-base.conf as suggested on one of the pages I went to, but it appears to have no effect.

• I tried installing PulseAudio, but no combination of PulseAudio and other settings worked.

EDIT2 Right, I've got it partially working, by following olejorgenb's steps:

• Unload all processes using the soundcard.

• Change to the directory where the file called vendor_name contains Realtek (on mine it's at /sys/devices/pci0000:00/0000:00:1b.0/sound/card0/hwC0D0)

• then as root do echo acer > modelname && echo 1 > reconfig

Restarting kmix then lets me unmute the sound and it works.

But how can I make this change stick?

EDIT3 As per olejorgenb's suggestion I've tried adding:

echo acer > "/sys/devices/pci0000:00/0000:00:1b.0/sound/card0/hwC0D0/modelname"
echo 1 > "/sys/devices/pci0000:00/0000:00:1b.0/sound/card0/hwC0D0/reconfig"
/usr/sbin/alsactl init

to /etc/rc.local which didn't work. Then I tried putting it in /etc/init.d/speech-dispatcher as this is one of the processes I have to kill to get sound working manually. I see the usual message about

Unknown hardware: "HDA-Intel" "Realtek ALC268" "HDA:10ec0268,1025011e,00100003  HDA:14f12c06,1025011e,00100000" "0x1025" "0x011e"
Hardware is initialized using a guess method

scroll past during startup, but still no sound.

Anymore suggestions from anyone, how to get my sound to come up automagically on startup?

SOLUTION: It turns out that the above was a red herring, the problem lay with the fact that I wasn't a member of the audio group (or possibly pulse or pulse-access) adding myself to this group, and logging back in (I may have been able to bypass the login but I wanted to make sure) restored working sound to my system.

Have the requirements for either the kernel or Alsa changed so that to make audio work, you now need to be a member of the audio group. Or have Debian made changes? Or did the update change my membership?

Depending on which of these is probably the cause, depends where I submit a bug to.

Thanks for all of your help.