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From: rfg@hound.UUCP (R.GRANTGES)
Newsgroups: net.audio
Subject: Re: hearing songs before they start
Message-ID: <596@hound.UUCP>
Date: Fri, 24-Aug-84 22:22:37 EDT
Article-I.D.: hound.596
Posted: Fri Aug 24 22:22:37 1984
Date-Received: Sat, 25-Aug-84 06:34:18 EDT
References: <2197@sdccsu3.UUCP>
Organization: AT&T Bell Labs, Holmdel NJ
Lines: 31

[.]
You are hearing "pre-echo". There is also "post-echo", but it is usually
masked by or heard as reverberation. There are two possible sources:
Recording at too high a level on the master disc, or (much less likely)
"print-through" on the master tape.
When the master disc is being cut by a stylus, if the stylus moves too
vigorously, it will push vinyl material over into the region of the next
groove. Instead of thinking of the master disk as rigid, think of it
as warm fudge when the cutting stylus comes along. If the grooves are
not far enough for the cutting volume,some of the modulation of one
groove will merge with that of the next. Remedy: space grooves farther
apart or reduce cutter excursion. Usually caused by sloppiness in
the disc mastering process.
When recording tape is wound on a reel (as it must be) the layers of
magnetic material are seperated only by the tape backing material and
the magnetic field of one layer will interact with the layers on each
side. Some of this interaction is permanent and is called "print-
through." How much of it occurs depends on lots of factors such as
heat, humidity, other magnetic fields, tape tension, materials used
for tape and backing and their thickness. Commercially this is not
usually bothersome because quality tapes are handled and stored
properly and recordings at 15 or 30 inches per second cause
adjacent layers of tape to have sound so closely spaced that it would
not be perceived as echo but rather as muddiness or distortion.
With amateur recordings made at slow tape speeds (especially cassettes
at 1 7/8 ips) this can be more of a problem. Depending on how the tape
is wound, the print-thru will appear as pre-echo or post echo.
Remedy: use good materials, proper tape handling and storage techniques.
Dick Grantges   hound!rfg