[LAU] Low mic recording level in Ubuntu

My mic recording level in Ubuntu+Gnome is frustratingly low. I have (I think) wound up all the levels to maximum in the mixer, but I still get only -20dB even with shouting into the mic. It's the same for all hardware (2 internal and 2 USB soundcards, different mics), 2 different computers, 2 different versions of Ubuntu (Heron on my desktop and Ibex on my laptop) and whatever recording software I use (arecord, audacity, kwave, ecasound). Also the same with Jack and if I kill pulseaudio. This started a few months ago (originally, when everything was first installed, it was fine) so I'm pretty confident it's an ALSA-related software issue. Seems like ALSA (or something) is being told to attenuate the signal somewhere. Any clues where to look? Peter Clarke