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From: rdp@teddy.UUCP
Newsgroups: net.audio
Subject: Re: Print-thru: Magnetic or Mechanical
Message-ID: <1623@teddy.UUCP>
Date: Mon, 11-Nov-85 11:07:38 EST
Article-I.D.: teddy.1623
Posted: Mon Nov 11 11:07:38 1985
Date-Received: Thu, 14-Nov-85 18:42:59 EST
References: <937@cvl.UUCP> <2860@wateng.UUCP>
Reply-To: rdp@teddy.UUCP (Richard D. Pierce)
Distribution: na
Organization: GenRad, Inc., Concord, Mass.
Lines: 29

In article <2860@wateng.UUCP> gtward@wateng.UUCP (Greg Ward) writes:
>>   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

Not entirely correct. In fact, the vertical modulation constitutes the
L-R signal, while the horizontal modulation constitutes L+R. When we
get all done figuring out how this mish-mash works, then we find that
indeed, one wall holds the right channel information, and the other
wall the left channel. The two channels are "out of phase" with one another
so that the rumble components (thought to be primarily vertical motions)
are playeed back out-of-phase.

For all intents and purposes, each wall holds one channel worth of information.