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These comments, and Jerry's web posting, are interesting.

For what it's worth, the folks at the Philips-Dupont plant in North Carolina told my mother she was 
not the only producer who could reliably identify which glass mastering machine cut a test press 
master. She could also reliably tell whether a test pressing came from North Carolina or Hanover, 
Germany. Very subtle differences were heard.  The North Carolina plant was run very well in the 90's 
and turned out typically high quality discs in huge numbers. The folks there said that CD 
replication is not a trivial matter and there are many variables that an effect the end product 
sound quality, much like LP cutting and pressing. Completely different variables, though.

David Chesky makes an interesting case for high-resolution downloads in the latest Absolute Sound 
issue. His point is that if you remove replicated silver discs and mechanical playback of those 
discs, you stand a better chance at having a reliably excellent-sounding digital product. I don't 
know if there's any science been done to prove this out, but another data-point is that the 
excellent-sounding Benchmark DAC, as well as a couple of other well-reviewed DACs, are built on the 
concept of removing jitter from a CD or DAT source by stripping out clocking information from the 
source data stream and re-clocking everything before converting to analog (in other words, assuming 
that all mechanical playback will introduce jitter and require re-clocking of the datastream). There 
are also scientific tests I've seen that show the USB output of a digital audio stream from most 
computer is laden with jitter. I've read in several places that jitter is very audible even to 
un-trained ears, if it's severe enough. Jitter was understood relatively early in the CD evolution, 
as was the preferability of dither on low-level signals. I think most DAW software introduces dither 
into bitrate down-conversion by default nowadays.

Is there any science on whether jitter from a CD drive can audibly effect a "rip" of that CD to MP3 
or other lossy-compressed formats? Since most "ripping" takes place at high speed (higher than 1x 
RPMs), I'm wondering if jitter plays any role, and if not what mechanical factors do effect the 
results? For instance, why do MP3's sound OK from a library-borrow disc that has such a heavy 
sticker on it that it clearly is having mechanical issues as it turns (the drive sounds like a 
little model airplane is in it)?

-- Tom Fine

----- Original Message ----- 
From: "Rob Poretti" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, November 19, 2010 9:30 AM
Subject: Re: [ARSCLIST] Listening Tests


> The only comment I would say is that the use of the word "golden ears" is a
> bit misleading as it is often associated with audiophiles.  It has been
> proven with significant research (read Floyd E Toole and others) that
> audiophiles, musicians, sound engineers and music producers - with similar
> hearing thresholds - were indistinguishable in "judgment variability" of
> subjective listening tests.
>
> In fact, the largest single variable that correlated to poor "judgment
> variability" was hearing loss... and unfortunately for us older guys - the
> biggest correlation to hearing loss was age...
>
>
> Cheers!
>
> _/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/
> _/
> Rob Poretti
> Sales Engineer - Archiving
> Cube-Tec North America LLC
> Vox.905.827.0741  Fax.905.901.9996  Cel.905.510.6785
> _/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/
> _/
>
>
> -----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.
>