Okay so I opened my case up yesterday to add in a couple of fans, and since then when I put my headphones in it sounds like the sound on the left headphone is slightly lower. I've tried it with a different set of headphones and it does the same thing.
I do have a sound card and I've checked the settings and both right and left are equal.
I'm just thinking could I have knocked the sound card when I opened the case yesterday? I'm not sure what else it could be.
Either the left ear is lower or right is louder.