Right Channel Volume Lower than Expected

[josephting]

Right channel sound reproduction has lower volume as expected (Left channel is louder than right channel).
Rebooting fixed it but the problem comes back a few hours later.
 
Using headphones port (front jack) to plugin my Sennheiser HD 449.

See spoiler for Xonar DX connectors.

 
Tested my headphones with my phone and there's no problem.

Plugging in my headphones to the sound card directly doesn't solve the problem so cable extension faulty is not the case.

(HD 449 comes with short cable length including a cable extension)
 
In conclusion, pretty sure it's sound card's fault or OS problem or driver's problem. (Not headphones or cable)
 
Anyone knows what's wrong with this?

[orangecat]

Try and RMA the card it is possible that one of the onboard chips is bad.