How to Change Left-Right Audio Balance [duplicate]
Install Pulse Audio Volume Control from the software center and run it:
You will get a screen like this:
If your balance sliders are locked together, click the lock in the upper right corner of the window and adjust the left and right balance volumes until you reach the point of satisfaction. For me that's about here:
If you then lock the lock again your adjustments will be locked in place and survive a reboot.