I've wasted many hours trying to find a solution to this problem but thought I'd would see if anyone here can help me before I give up. Here is my situation:
1) A while back my laptop's headphone jack became unusable (technically it still works but sound comes through both the laptop speakers and the headphones)
2) As a workaround I bought some USB audio adapters online, which gave me a working headphone jack through USB.
3) This worked great for a while but recently the adapter I was using stopped working.
4) I tried one of the other ones I had (same idea but a different type - this one a "3D sound" adapter). It worked but sound only comes through one side of the headphones.
5) I tried the headphones elsewhere but they worked fine, and tried another set of headphones too. Then I tried another USB adapter that I had been using before until the cord became loose (it still works but is very finnicky based on the position of the cord, so I stopped using it). The sound still only came out of one side of the headphones.
So, it seems like the 3D sound adapter has permanently messed up the balance when connecting headphones through USB. I tried altering the balance found by going to Control Panel->Sound but it shows equal balance there. I also tried uninstalling all USB devices and then installing it again, but still the same problem.
Anyways, not very hopeful here but please let me know if you do have any ideas,