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From: gvcormack@watmum.UUCP (Gordon V. Cormack)
Newsgroups: net.audio
Subject: Re: Print-thru: Magnetic or Mechanical
Message-ID: <326@watmum.UUCP>
Date: Fri, 8-Nov-85 16:03:55 EST
Article-I.D.: watmum.326
Posted: Fri Nov  8 16:03:55 1985
Date-Received: Thu, 14-Nov-85 01:26:22 EST
References: <937@cvl.UUCP> <2860@wateng.UUCP>
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Organization: U of Waterloo, Ontario
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> >   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)
> 
> Your argument for why mechanical print through would be stronger on one
> channel then the other is incorrect. You seem to be suggesting that each
> channel is recorded on a different side of the groove. In fact, how the
> two channels are multiplexed in the groove is that one channel is
> recorded in the side to side variations of the groove, and the other is
> recorded in the up and down variations.
> 
>                             - Greg Ward

Sorry.  This is wrong, too.  The two channels are recorded in orthogonal
directions, but one is angled 45 degrees from vertical in one direction
and the other is angled 45 degrees in the other direction.  The phase
is applied so that the horizontal components of the two signals are
in phase and the vertical components are 180 degrees out of phase.
If you insist, this can also be thought of as recording L+R 
horizontally and L-R vertically.