Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site watdcsu.UUCP 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.... UUCP: {decvax|utzoo|ihnp4|allegra|clyde}!watmath!water!watdcsu!herbie CSNET: herbie%watdcsu@waterloo.csnet ARPA: herbie%watdcsu%waterloo.csnet@csnet-relay.arpa NETNORTH, BITNET, EARN: herbie@watdcs, herbie@watdcsu