Hands up who can really hear dither?!
That shouldn't do it. Unless for some odd reason your current sound card doesn't play anything lower than around -90 dB. The very nature of dither is so that it is NOT heard. If your really want to hear dither though try listening to 8 bit, highly noise shaped dither and you should easily hear a piercing HF noise.I always use dithering maybe cause I can't tell much difference in sound. Maybe I need a better Sound Card?