I blew my laptop sound card somehow. Not sure why it blew, but it was working fine until I plugged a mic pre-amp into its mic socket to record some voice. Strange thing is, I have done this before many many times with the same settings, input mic, voltage supply, and its never complained before. This time however, it's blown it, it seems. And it's not a separate board, but built into the motherboard.
Obviously a re-boot hasn't solved the problem. Neither did trying to play audio via Linux instead of Windows. So it has to be a hardware failure. But the symptoms are not normal. If it had been a case that I had whacked too much power into the input, I would expect the initial amplifier stage to fail resulting in mostly just very low output audio levels. But what I get is more like I blew the speakers on a home stereo by turning up the volume far too loud. It sounds really raspy like the speaker coils have partly decatched from their cones! Tried using known-good earphones from the earphone socket, but the result is the same.
I am gonna have to trash this lappie if someone here can't think of something I might have overlooked. Any suggestions?