ASUS Xonar STX - Distortion

Hi there, has anyone here had any issues with these brand of cards producing distortion? Im getting it only on low frequency bass only. both through the RCA outs and direct to headphones.

I just got my B&W 802 DIAMONDS hooked up to my PC then this started, or maybe it was always there as i was using an active sub which probably didnt have the definition to show the bass distortion.

any thoights what the issue could be?

Ive updated the drivers to the latest. next test is to totally remove the card and see if the on board sound does the same thing.

any thought would be appreciated.
(1)have you used the Asus control panel to make sure enhancements (ha!) are disabled?
2) Are you feeding analog out or using digital to a DAC?
3)Highly recommend that you use Jplay so long as your source music is lossless as that will improve various bad things in PC playback with lossless music and good player like Jplay and Foobar
after a long hard road of elimination and reading and blowing up one 802d speaker i discovered it was windows media player. something to do with the codecs changed to VLC and its all good.

I haven't been able to fix the problem with WMP either