[Chris J]

Oh man, I suspect that sound card is not the world's greatest soundcard.
I'm quite surprised that inserting a 47 ohm resistor helps things.
Personally, I want a solid state headphone amp to have a very low output impedance.
You actually rasied the output impedance by 47 ohms.

 

[NAeternal]

Well, i sold it and returned to the onboard one.

Creative X-Fi Go Pro, I really dont recommend this card. That buzzing on low impedance headphones, and dark sound...

I'll never go for an usb card again, never.