Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/5/84; site cvl.UUCP Path: utzoo!decvax!decuac!cvl!jc From: jc@cvl.UUCP (John Canning) Newsgroups: net.audio Subject: Print-thru: Magnetic or Mechanical Message-ID: <937@cvl.UUCP> Date: Thu, 7-Nov-85 11:53:24 EST Article-I.D.: cvl.937 Posted: Thu Nov 7 11:53:24 1985 Date-Received: Fri, 8-Nov-85 01:57:05 EST Distribution: na Organization: Computer Vision Lab, U. of Maryland, College Park Lines: 28 Several recent net.audio postings have talked about print-thru problems on vinyl disks. I've always thought that 'pre-echo' was due to the music etched into the next groove of the record affecting the groove in which the needle is located. It seems unlikely to me that the very weak permanent magnetic fields emanating from a layer of tape could affect the adjoining tape layers on the reel. If it is a magnetic phenomenon, then the way in which the reel is wound should have litte effect on the print thru because the adjoining layers of tape have just reversed position. The magnetic particles are on only one side of the tape, but the distances between layers remain the same. Thus, depending on winding direction one would get either pre-echo or post-echo. Post-echo may not be as easy to detect because the sound usually has a longer decay time than rise time and the ear can't adjust to hear faint sounds after a loud passage. The pre-echo time delay constant would be a function of the position on the tape of the music since the reel diameter (and circumference) vary with position (and change order when wound backwards). If it is a mechanical phenomenon, then it should be stronger in one channel (the channel etched on the side adjoining the next groove) than the other. The record should also be in the same orientation at the onset of the pre-echo and at the onset of the corresponding music. Since I don't have any records with noticeable print-thru, I'd be interested to hear if other people's print-thru satifies/doesn't satisfy these conditions. - John Canning (jc@cvl.umd.edu.arpa)