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Path: utzoo!watmath!watnot!watdcsu!herbie
From: herbie@watdcsu.UUCP (Herb Chong - DCS)
Newsgroups: net.audio
Subject: Re: Digital Trojan Horse?
Message-ID: <1628@watdcsu.UUCP>
Date: Fri, 23-Aug-85 14:39:51 EDT
Article-I.D.: watdcsu.1628
Posted: Fri Aug 23 14:39:51 1985
Date-Received: Sat, 24-Aug-85 19:14:45 EDT
References: <4189@alice.UUCP>
Reply-To: herbie@watdcsu.UUCP (Herb Chong - DCS)
Organization: U of Waterloo
Lines: 33
Summary: 

In article <4189@alice.UUCP> dsj@alice.UUCP (David S. Johnson) writes:
>This hypothesis is argued in Neil Levenson's audiophile column
>in the May/June 1985 issue of FANFARE (Levenson is a golden ear
>who would do THE ABSOLUTE SOUND proud).  He claims that digitally
>recorded vinyl discs generate ultrasonic products not present
>in analogue discs (he claims these have been measured), which
>somehow cause micro-cracks in turntable bearings (he claims
>these have been seen under electron microscopes) which by some
>mechanism greatly increase the short-term speed irregularities
>of the turntable, especially audible on piano music.

digital audio depends on filtering of both input and output to remove
high frequencies or else there'll be severe aliasing problems.  on
playback, the recorders use enough of a high frequency filter that a
good analog recording will also have the same ultrasonic energy.  the
cutter heads themselves resonate at a frquency of about 35kHz response
and can be excited by a typical high frequency signal, whether
digitally produced or analog.  another thing too is that surface wear
mechanisms of things like bearings is still poorly understood and an
area of active research.  unless the guy has a a PhD in materials
science, i can't believe his claims of ultrasonic signals causing the
cracks.  they will have the effects he describes though, as the flutter
will increase if the cracks get big enough, but more likely the result
will be increased rumble.

Herb Chong...

I'm user-friendly -- I don't byte, I nybble....

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