Dither

The Cara release of DS firmware saw the introduction of a new dithering process to the DS audio path.

The DS upsampler has an internal processing resolution of 35 bits, but this must be reduced to 24 bits to match the resolution of the DAC.  Previously this had been achieved by simple truncation, but this created quantization distortion (albeit at a very low level).  In Cara, this distortion mechanism was eliminated by adding a carefully calculated dither signal before the truncation. This effectively preserves the audio information present in the 35 bit upsampled signal at the expense of a small increase in noise floor.