generally, you can design a random (or pseudo random) sequence generator. you can vary the length of shift register to achieve better results. then add it to your modulator to make your signal busy enough.
A SD modulator with 1-bit output and n-bit input could be controlled by an additional 1bit-dither input. Because the mean value of the dither sequence is 0.5 a systematic difference exist. For audio application it is not important.