On 30 Jan 2004 01:46:58 GMT, Steven Sullivan wrote:

Stewart Pinkerton wrote:
On 29 Jan 2004 20:29:55 GMT, Steven Sullivan wrote:

Stewart, what do you make of the technical results of
comparing one-box vs
separates in this paper, where Dunn et al conclude that
disc- or player-related sampling
jitter is NOT the cause of the distortion observed in their
measurements of one-box players?

http://www.prismsound.com/downloads/cdinvest.pdf

I don't see anything relevant there, and as it happens, I was one of
the 'postal votes'. Note that there is well-documented evidence of
significantly lower jitter in one-box players from many years of Paul
Miller's technical tests in HFN.

But Dennis et al. seem to find that jitter isn't the culprit of
the spuriae they measured specifically in one-box players;
they attribute that to 'amplitude modulation
of the analog outputs by motor- and servo-related interference'.
See the section 'Measurement of Spuriae'
and the first few paragraphs of the Conclusion. It appears,
unless I've misunderstodd the paper, that
one-box systems measured consistently worse than two-box systems
in their tests. The distortion is posited to be audible
(see paragaph 1 of the Conclusion) though
the audibility of the distortion was not
directly tested.

OK, I see what you're getting at. Please note that this is certainly a
matter of implementation, and the authors do note that it's not too
difficult to address. The one-box player they used was a Marantz
CD-63, and I doubt that even its most ardent fan would claim that this
represents the state of the art! Compare and contrast with say the
Arcam CD-23 or especially any of the Meridian players, and you'll see
that this effect is essentially absent.

If you recall, there was considerable discussion about the sound
quality of CD-R when it came out, and it was noted that on some
players, the copy sounded *better* than the original! This was traced
to the 'wobble track' on the CD-R being easier for the servo circuits
to track, and Martin Colloms noted that the sound degradation was
exactly due to amplitude modulation from the servo circuits finding
its way into the analogue output. He also discovered that better
players did not demonstrate this effect. Note that Prism Sound don't
make a one-box player, do make excellent jitter-reducing DACs, and
seem to have extrapolated their findings on one cheap one-box player
to *all* one-box players. A step too far, methinks.

Anyway, I have to go now, as I'm off to India for a couple of weeks.
Well timed, as it's snowing here!
--

Stewart Pinkerton | Music is Art - Audio is Engineering