equ causes fussy bass you-pax extreme audio 1.01

Hi all, I have an x-fi xtreme audio card and have been using the youp-pax xtreme audio 1.01 drivers for the last few months. All runs well and sound is clearer in general compared to creative's drivers. The only problem is when I am using the equaliser any kind music with heavy bass and movies with bass effects have a fuzzy sound to them, the effect is more obvious if i boost bass in the EQ. I know it isn't distortion because most of the time I keep sound levels down low. (around a third)