Print

Print


Comments remind me of the old phrase "that is all well and good in practice
but it will never work in theory." Although I have not personally verified
it, the reported quality issue is most likely valid whether readers want to
believe it or not. It was introduced simply to point out that a critical
listener may detect something that our test equipments do not.

Mass storage devices such as tape, floppy, HDD, CD, DVD, etc. are
self-clocking where the read clock is phase locked to the incoming bit
stream. Intermittent speed variation (ISV) has been and always will be a
problem because the PLL is bandwidth limited and cannot track high frequency
ISV.

Early CD and DVD drives were constant linear velocity (CLV) where read data
frequency was a constant across the disc. High speeds require constant
angular velocity (CAV) at part or all of the disc resulting in varying data
rates, placing greater demands on the data clock PLL and creating even more
sensitivity to ISV.

Jerry Hartke
Media Sciences, Inc. 

> -----Original Message-----
> From: Association for Recorded Sound Discussion List
> [mailto:[log in to unmask]] On Behalf Of Shai Drori
> Sent: Friday, November 19, 2010 4:58 PM
> To: [log in to unmask]
> Subject: Re: [ARSCLIST] Listening Tests
> 
> Sorry to be the party pooper, but the rotational speed has no affect on
> the playback. Since no one (at Philips or Sony) had intended to attempt
> to build a transport stable enough to stream the digital numbers  in the
> speed they were to be played, not to mention the fact that they are read
> off the disn scrambled by the error correction scheme on purpose. All
> players have a buffer that also rearranges the bits in the correct order
> and then re-clocks them with the internal clock. A faulty glass master
> would maybe make a faulty CD altogether but in normal cd operation the
> rotational speed stability is not a factor beyond a certain standard.
> Shai Drori
> 
> On 11/19/2010 6:21 PM, Mike Gray wrote:
> > Think carefully about this: both the clock signal and the audio data
> > are being altered at each RPM; not good for analog audio, not good for
> > digital.  Bottom line: clock errors, random or otherwise, simply must
> > be corrected at replay.  And BTW, I love my Benchmark, too.
> >
> > Mike Gray
> >
> > Alex Hartov wrote:
> >> Hi Folks
> >>
> >> Sometimes I have to express serious doubts about what I read.  From
> >> the given URL I read the following:
> >>
> >> "Many years ago, an irate musician contacted his CD-DA replicator
> >> claiming that his latest release was of poor quality. Extensive
> >> electrical, mechanical, and listening tests by the replicator failed
> >> to disclose any flaws while the musician became angrier. The
> >> persistent replicator finally identified a defective glass mastering
> >> turntable in which one coil of its brushless DC motor had failed,
> >> causing an imperceptable once- around speed variation. After repair,
> >> the musician declared his satisfaction in the resulting high CD-DA
> >> quality."
> >>
> >> Is anyone suggesting that fluctuation in the rotating of the disc
> >> itself can have ANY effect on playback?  Do I misunderstand
> >> something?  Since the data stream is buffered the speed with which it
> >> is read from the disc cannot possibly have any effect on the playback
> >> speed which is controlled by the DAC clock.  So what is the above
> >> quote intended to convey?
> >>
> >> Alex Hartov
> >>
> >> On Nov 19, 2010, at 9:30 AM, Rob Poretti wrote:
> >>
> >>> -----Original Message-----
> >>> From: Association for Recorded Sound Discussion List
> >>> [mailto:[log in to unmask]] On Behalf Of Jerry Hartke
> >>> Sent: November 18, 2010 8:10 PM
> >>> To: [log in to unmask]
> >>> Subject: [ARSCLIST] Listening Tests
> >>>
> >>> Input on the subject has been posted at:
> >>>
> >>> www.mscience.com/faq35.html
> >>>
> >>> Jerry
> >>> Media Sciences, Inc.
> >