Hi Graeme,
Thank you for sharing the article, it's interesting. The author got a surprising amount of benefit from high-frequency dithering the eight-bit samples. You can partially demonstrate this effect with your -1452 mini eval board. The circuit below boosts the audio level to 30 bits (I left two extra bits for headroom). Then you adjust attenuation as desired, after which the dithering is added. Next it purposely decimates this signal by shifting the last 16 bits overboard. If you set the attenuator to -60 dB or so, there aren't many bits left and you can hear the quantization effect. Switching the noise (dither) source ON makes it sound better, although the dither in this case is in-band and thus audible. The eval board's AD1938 codec is hardwired for 48KHz, thus we cannot explore the further benefit of 192KHz operation with ultrasonic dither.
Image may be NSFW.
Clik here to view.
Note that many A-D and D-A converters, though accommodating 24 bits-wide signals, do not actually perform to that level. 24 bits implies a dynamic range of about 144dB, but for example the AD1938 codec is rated for about 110dB (about 19 bits worth). Thus in practice you can lose a few bits and not hear the difference at all.
Best regards,
Bob
