Sennheiser 598 Left driver louder?

After recently purchasing the Sennheiser 598's, I have come to notice that when listening to music, the left driver is louder than the right. I also use a Fiio 10k amp/dac to power them. Should I send them back or is this normal?

Much Appreciated,

I would simply suggest you plug in some other headphones to the Fiio amp just to make sure that the amp is not causing the issue.

If you can prove the amp is not the issue, then I would definitely send them back.