However when I plug a line-level audio signal into the
soundcard's 'mic' mini-jack and try to record a wav audio
file I get nothing. (I can hear the sound fine through the
headphones/laptop speakers). I've tried 'wavtools' and
'ecasound' but when I try to play back the resulting wav
file using 'Alsaplayer' all I get is silence.
Try qarecord. It's really great for a quick recording.
Or audacity for instant editing the recorded signal.
Best regards
ce