Check your "stylus rake angle". This is the angle at which the stylus is actually contacting the record groove.
If you back-light your stylus, you should be able to see the little diamond shaft that is on the tip of the cantilever. This should be straight up and down when it is in the record groove. If it tilts forward at the top, then it is going to make bad sound like you are hearing. I'd suggest a slight lowering of the tonearm VTA adjusment to counter this, and improve your sound.
If you back-light your stylus, you should be able to see the little diamond shaft that is on the tip of the cantilever. This should be straight up and down when it is in the record groove. If it tilts forward at the top, then it is going to make bad sound like you are hearing. I'd suggest a slight lowering of the tonearm VTA adjusment to counter this, and improve your sound.