USB turntable
 

On 2006-12-17, Glenn Richards wrote:
John Phillips wrote:

I was thinking about that. Normally a source with its own high-enough
noise floor, as long as the noise is not correlated with the signal,
should see no benefits from turning on noise shaping for the dither.

Interesting theory, borne out by something I discovered a few years ago...
...
The analogue copies sounded better. Far fewer MP3 compression artefacts.
...
Which, I can only assume, was because of the higher noise floor on those
tracks causing a noise shaping effect. Therefore covering up the
compression artefacts.
...

I believe you are thinking of a different effect. The question I was
responding to was about SBM. This is a dither noise that is applied
to the an analogue signal just before the A/D converter, to eliminate
quantization distortion. SBM is a way to noise-shape that dither (at
circa 93 dB below full scale in 16-bit systems) to make it less audible
and allow lower level signals (down to circa 115 dB below full scale)
to be audibly encoded on the CD.

I think your point is about the effect of noise on MP3 encoding - which
is a matter I have never investigated so I can't comment.

--
John Phillips