Comment 35 for bug 441195

Found a workaround for the Inspiron 9400 on Lucid based on Cristian's "analog-output-lfe-on-mono.conf" fix.

1. Edit the file "analog-output-lfe-on-mono.conf" (sudo gedit /usr/share/pulseaudio/alsa-mixer/paths/analog-output-lfe-on-mono.conf)

Change:

[Element Hardware Master]
switch = mute
volume = merge
override-map.1 = all
override-map.2 = all-left,all-right

[Element Master]
switch = mute
volume = merge
override-map.1 = all-no-lfe
override-map.2 = all-left,all-right

[Element Master Mono]
required = any
switch = mute
volume = merge
override-map.1 = lfe
override-map.2 = lfe,lfe

Into:

[Element PCM]
switch = mute
volume = merge
override-map.1 = all
override-map.2 = all-left,all-right

[Element LFE]
switch = mute
volume = merge
override-map.1 = lfe
override-map.2 = lfe,lfe

[Element Master]
switch = mute
volume = merge
override-map.1 = all
override-map.2 = all-left,all-right

Remove:

[Element LFE]
switch = off
volume = off

2. Restart pulseaudio (pulseaudio -k).

3. Open sound preferences and choose from the output tab the "Analog Output (LFE)" connector.

This fixed it for me. Sound works like it should do again, enjoy!