fireberd said:
The M-Audio Fast track Ultra is a "USB sound card" and no distortion according to the users post above yours.

I'm at the point there is some type of hardware problem.
As I now made it work with a usb sound card, I will now try to boot from a usb-bootable windows 7 to check that windows 7 has a clear headphone audio with the generic driver. If that is confirmed, I do not know what else can be done.