The internal mic for the Dell XPS M1330 has had continuous problems in Ubuntu, but Karmic Koala has seemed to have the fix. Right now there is no need to change the kernel or do anything drastic with alsa. There is only a need to make a few minor changes to the sound preferences.
The fix is an easy change in pulseaudio. Ubuntu 9.10 has a new sound applet, so just right click the sound icon in the notification area and select Sound Preferences. Select the Hardware tab. At the bottom of the window, you should see a dropdown box next to word Profile. Click on this and select “Analog Surround 4.0 Output + Analog Stereo Input”. Now, click on the input tab. Raise the input volume to the maximum it can go. Make sure the Connector is “Microphone 1”. You may close the window. You now have a working sound input.
Quick note: The sound input may still be a little low but it shouldn’t be a deal breaker. I have not had the need to raise it the volume further.
I purchased a Dell XPS m1330 system over a year ago and installed Ubuntu the instant that I received the laptop. There have been little bugs here and there that I have been able to workaround successfully for some time, but I started having problems with the microphone that I was unable to fix beginning when pulseaudio was introduced to Ubuntu Intrepid 8.10. This led to this bug: https://bugs.launchpad.net/fedora/+source/alsa-lib/+bug/275998
After a few months of participating in the bug we ended up happiest with upgrading the kernel to 184.108.40.206. To do this I had to upgrade nvidia binary driver to 180.60 because the current one will not work with the jaunty kernel. Sound is definitely better because I don’t get crackling anymore and latency issues as far as I can tell. We hassled the PulseAudio developer for the bug, but it seems it may have not been his problem. Still when I upgraded, the sound was still low on the mic. You have to boost it through paman. You need to have this installed to do this. Once installed you type paman in the terminal and you select the devices tab and select the device that has capture in it. Select properties and adjust the volume. I was satisfied with the volume at 150%. I definitely had a better quality input. Since things work much better for me. There is no support for this, so be aware of that. Make sure to get rid of any workarounds to get this working. I hope this helps.
First install the nvidia driver if needed… I have m1330, so I needed it. Install in order from this mirror since the archive for ubuntu no longer has it: http://mirror.linux.org.mt/ubuntu/pool/restricted/n/nvidia-graphics-drivers-180/
nvidia-180-kernel-source_180.60-0ubuntu1_i386.deb nvidia-180-libvdpau_180.60-0ubuntu1_i386.deb nvidia-glx-180_180.60-0ubuntu1_i386.deb
Install the kernel in order from here that I give for packages: http://kernel.ubuntu.com/~kernel-ppa/mainline/v220.127.116.11/
linux-headers-2.6.30-02063004_2.6.30-02063004_all.deb linux-headers-2.6.30-02063004-generic_2.6.30-02063004_i386.deb (or amd64) linux-image-2.6.30-02063004-generic_2.6.30-02063004_i386.deb (or amd64)
Once all this is installed you can restart and everything should be functioning. You can adjust the mic sound through paman, as I had discussed before in the devices tab and click on properties for the input source. Set skype to pulse to get it working.
Edit: I changed the mirror for the nvidia drivers. The one I had previously, no longer had the files.