PSP X-Dither is a mastering dither and noise shaping processor (VST, RTAS and AAX for Windows; AudioUnit, VST, RTAS and AAX for Mac OSX). It is designed to cover wide range of situations when dithering or noise shaping is the way to maintain the quality of an original mix, group or individual track during various stages of the recording and mastering process, including final digital mastering.

I didn't think anyone could achieve what PSP has achieved with PSP X-dither: They've created a selection of noise-shapes which allow me to create a 16-bit result that sounds almost identical to the 24-bit source. With other dithering algorithms I often have to compromise, making a sound which distorts the tonality of the original source, or weakens the depth, or softens the transients. But with PSP X-dither I can easily find the perfect shape for the music I'm working with.

Bob Katz, President, Mastering Engineer, Digital Domain ; Author of the Mastering Audio - The Art And The Science