[BC] CD vs LP

[Robert Orban]

If you measure the maximum sinewave level that the channel can 
accommodate using an RMS detector, you also need to measure the 
dithered noise floor using an RMS detector. Just to verify, before 
posting this message I measured the output noise floor of an Optimod 
6300 in TONE mode with dither turned on as -92 dBfs RMS and measured 
the maximum undistorted sinewave output as 0 dBfs RMS on the same meter.

The 6300, like all Optimods, uses first-order highpass TPDF dither. 
To make sure that the dither was working as expected to decorrelate 
the noise from the signal, I also checked the THD+N with a -40 dBfs 
sinewave. It was -52 dBr, where the reference is -40 dBfs. None of 
these measurements support your claim that the dynamic range is only 
87 dB for 16-bit digital.

Meter was an NTI Digilyzer.

Please see the references in the Dunn paper, particularly the 
Lipshitz and Vanderkooy papers (refs [2] and [3]), which are 
considered classic.

At 04:49 PM 9/22/2008, RichardBJohnson at comcast.net wrote:
>Yes I know and it's wrong. It's often quoted as 20 log10 * 65536 for
>65536 codes of a 16-bit number, which is about 96 dB.
>I show how it is wrong because it can't possibly be greater
>than 20 log10 * 32767  (90 dB) even if you consider the peakshitz &
>value (incorrectly) as having something to do with dynamic
>range.
>
>--
>Cheers,
>Richard B. Johnson
>Read about my book
>http://www.LymanSchool.org
>
>
>  -------------- Original message ----------------------
>From: Robert Orban <rorban at earthlink.net>
> > At 08:09 AM 9/22/2008, RichardBJohnson at comcast.net wrote:
> > >0.707 * 32767 =  23,166 (convert peak level to RMS)
> > >20 log10 (23,166) = 87 dB
> > >
> > >Eighty-seven decibels dynamic range  is much greater than
> > >typical analog audio circuitry that almost never exceeds
> > >80 dB over a 20 kHz bandwidth, that it should not be the
> > >limiting factor in a high-fidelity system.
> >
> > Dunn says it is 93.3 dB with flat  (white) TPDF dither in the AES
> > Convention presentation:
> >
> > www.nanophon.com/audio/dynrange.pdf
> >