From: Peter Alcibiades palcibiades-first@yahoo.co.uk
Disconnect the mike, and try to play back? Error message.
Restart audacity? Now playback works, but recording does not. What appears to happen on attempting to record is that the track seems to be trying to playback through the mic. Well, this is my interpretation of what is visible and audible.
Probably correct Peter: I suspect the chipset used in the mic is bi-directional (I have a similar issue with an audio+video grabber that also claims to have audio out but no connectors).
You should be able to select the appropriate recording device in the mixer applet (KDE or GNOME versions), and should also be able to see what channels your various audio devices claim to have. It's also worth checking what audio subsystem audacity is trying to use, it's probably Alsa for recording, but may be Jack or Pulseaudio depending on versions and audio arrangements in your distro. If audacity isn't using Alsa directly then you need to configure the appropriate sound server (Jack or Pulseaudio) inputs to use the correct underlying Alsa device for recording.
Finally - be aware that USB audio devices can come up in any order, so if you want the external sound card to always be device 0 (Alsa hw:0), with or without the mic plugged in, you will need to edit the udev rules to identify each USB device and fix the numbering (this is tricker if >1 device use the same chipset and thus have the same USB vendor and device IDs, although I have been able to make this work using bus IDs instead).
For all this GIYF :)
Phil.