I believe mic boost is on by default. What model are you running this as? Laptop or Fujitsu?

Tobin

I'm running it as model 'laptop'.

Any other hint at what might be causing this different behavior depending on the mic being stereo or mono, then?

In case someone needs it, I'll write again the quick description of the problem:

alsa-driver-1.0.14: playback: ok recording: stereo mic: ok mono mic: no input at all (very high volume already tried)

alsa-driver-1.0.15rc1: playback: ok (even better than with alsa-driver-1.0.14) recording: stereo mic: ok (seems better than with alsa-driver-1.0.14) mono mic: *very* very low volume, bad quality, lots of low-volume noise, too.

Thanks a lot, Pablo