I stumbled upon your post while looking for a fix for the same problem.
Basically, the snd-hda-intel driver supports quite a lot of different
soundcards all based on the same general chipset. There are maybe a
dozen of variants of this card that have different types of jacks (3
jacks, 5 jacks, surround capabilities, digital out, etc) . If your have
the same problem as I do (Dell inspiron 1300), then your microphone
jack doubles as a line-in jack.
This means that the driver has to tell the card if the internal
amplifier for the mic has to be enabled or not (depending if it's a mic
or not). The alsa drivers don't detect this "feature" so we can't
enable/disable it, because we can't interact with the setting. So the
amplifier is always off.
To know if you have "this" problem, plug in a mic, start recording,
_yell_ like crazy, and listen to the recording. You should hear a faint
noise, as if you were listening to someone at the bottom of a well. :(
Good luck finding the solution and if you do, please let me know ! :)