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Re: [ARSCLIST] "Record Club" CD's redux

From: Patent Tactics, George Brock-Nannestad

Tom Fine wrote about "flimsier" discs, and Jerry Hartke responded:

> I would be surprised if bit jitter resulted in audible differences. High
> bit
> jitter usually produces small, short duration read errors that are easily
> corrected by the first level of CD-DA error correction.
> Electrical, optical, and mechanical quality is important, and it seems
> that
> comprehensive tests have not been conducted. If you wish, I would conduct
> such tests at no charge on two "identical" discs, one original label and a
> second that sounds worse. Our test results are traceable to the Philips
> lab.
> Our address is at www.mscience.com/contact.html
> Jerry
> Media Sciences, Inc.

----- now, the "flimsiest" of discs imagineable is no disc at all, i.e. no 
transparent material (the polycarbonate alloy used) between the pits and the 
reading head that has to focus on the land. This is the case when a (nickel) 
stamper is being read. In order that the optics used for reading a 
standardized CD with a specified ray path through the transparent material 
can still be used, Audio Developments interpose a slab of glass (I think!) of 
the correct optical path length between reading head and modulated surface in 
their analyzers.

----- If it were imagineable that a flimsier (possibly meaning thinner?) 
plastic body could be used for some commercial CDs, then the signal-to-noise 
ratio would be much worsened, i.e. the high frequency signal would be 
defective. So it would not really be a jitter question, but rather bad 
detection. It is so long since I read the Red Book (a pirated copy) that I do 
not remember clearly, but I do think that the thickness and refraction index 
are specified in some manner.

----- it will be interesting to read what Jerry finds!

Kind regards,


> > -----Original Message-----
> > From: Association for Recorded Sound Discussion List
> > [mailto:ARSCLIST@xxxxxxx] On Behalf Of Tom Fine
> > Sent: Thursday, April 24, 2008 8:24 AM
> > To: ARSCLIST@xxxxxxxxxxxxxxxx
> > Subject: [ARSCLIST] "Record Club" CD's redux
> > 
> > We briefly discussed this topic a while back, whether Yourmusic.com (BMG
> > club) CD's are 100% the
> > same as off-the-shelf original-label. Bob Katz, in my estimation, is not
> > an audiophool nor a moron,
> > so his analysis counts for something:
> > http://www.stereophile.com/features/55/index.html
> > 
> > The jitter issue raises a couple of questions:
> > 
> > 1. would this trigger more error-correction in the playback system and
> > hence the perceived
> > "different" sound qualities?
> > 
> > 2. if one grabbed the same cut from the BMG and original-issue CD's with
> > Exact Audio Copy, assuming
> > EAC reported about the same quality percent from the grabs, would you
> have
> > identical-sounding files
> > on your hard drive?
> > 
> > For what it's worth, my observation about some BMG-club CD's is that the
> > discs seem to be flimsy,
> > especially compared to original-issue Polygram from the early and mid
> > 1990's. I wonder if they are
> > chinsy enough to trigger playback error-correction? That said, in my
> > playback system, I can't tell
> > any sound difference between BMG-club and store-bought of a few Blue
> Note
> > jazz reissues I recently
> > compared. I borrowed BMG-club of a few Mercurys and will compare when
> they
> > arrive.
> > 
> > -- Tom Fine

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