When I plug my headphones into my late 2008 (the aluminum one) MacBook's audio port, the right channel is louder than the left channel to the extent that it's pretty bothersome. Here are some things that may be relevant: 1. I don't know if one has become louder, or the other has become quieter. All I know is that the volume of the left is quieter than the right. 2. Up until this point the sound would get staticky if the headphones plug was moved around, but now that doesn't happen. 3. For a long time, during the static problem and now as well, the headphone plug comes out of the jack very easily, and if it comes out just the tiniest bit, audio will go back to playing through the built in speakers. 4. I've tried 2 other pairs of headphones, and have still run into the same problem. One of them was USB powered and that didn't seem to make a difference. I have a usb to audio port device, but that hasn't worked since I've installed el capitan. Aside from that, I've realized that it takes up two usb ports due to its size, which is problematic.