I have searched for something similar, but couldn’t find anything. I’m using Audacity 2.0.5 with Ubuntu 14.04.2
I have created two tracks and made one as left channel and one as right channel. Then I generate something on each of them. When I try to play them on headphones, I only hear the right track/channel. If I mute it, I don’t hear anything at all. The meter shows the left channel as working, but there’s no output. I have a HiFi amplifier plugged to the USB of the computer. Amazingly enough, if I send the audio to the USB amplifier, I can hear both channels on the speakers, but when I plug headphones to the amplifier itself, it still gives me only the right channel. I have already ruled out a malfunction in the headphones: they play fine with music both from the computer and from the amplifier, both with mp3 and with CDs. On the computer, the sound settings say “Front Left” and “Front Right” when I check the headphones, which means the computer is indeed stereo on the headphones and outputting right.
The behavior is the same if I set the tracks as mono or if I mix them up as one stereo track: by panning to the left channel, the meter moves, but there is no sound on the headphones, whereas there is sound from the left speaker only from the amplifier (as expected).
This contradicts my little understanding of the laws of physics and I’m completely out of clue. What could I try next?