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The PLL clock in the read drive that controls both the bit detector and the
spindle motor has a finite response time. Faster variations in the recorded
information are not compensated within this loop. In general, the motors
used for glass mastering are of much higher quality and may have many more
poles than those in commercial players, therefore the failure of one pole
can induce variations that are outside of the read PLL bandwidth.

Jerry 

> -----Original Message-----
> From: Association for Recorded Sound Discussion List
> [mailto:[log in to unmask]] On Behalf Of Alex Hartov
> Sent: Friday, November 19, 2010 10:28 AM
> To: [log in to unmask]
> Subject: Re: [ARSCLIST] Listening Tests
> 
> 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.