From: utzoo!decvax!harpo!ihnp4!ixn5c!inuxc!pur-ee!uiucdcs!emrath
Newsgroups: net.audio
Title: Re: Why it might not be good to demagnet - (nf)
Article-I.D.: uiucdcs.1292
Posted: Tue Jan  4 18:25:17 1983
Received: Wed Jan  5 03:15:22 1983

#R:rocheste:-36000:uiucdcs:22700006:000:1176
uiucdcs!emrath    Jan  4 15:57:00 1983

I think tape head demagnetization is a throwback to days when things
like DC bias were used and demag was necessary. I have tried making
careful measurements in my lab of the effects of demagnetizing heads
and so far have yet to be able to measure any (much less hear them).
Note that I have successfully measured noise outputs down to about
5 microvolts (100dB S/N re .5V, the eia std). I am fairly confident that
I am not washing out tape deck differences (before/after demag) with my
measurement techniques, unless those differences are less than 1 or 2dB,
which are insignificant. The difference between various brands of tape
can be greater than this. I bought one of those TDK jobs and it had a nice
booklet explaining what specs MIGHT be affected by using it, but I sure
couldn't measure any change. My belief is that the deck simply doesn't
(and never will) need demagnetizing. I have read every recent article in
the trade rags about head demagnetizing and they all seem to conclude that
nobody really knows for sure whether head demag is necessary, but it
doesn't hurt. I say, if it doesn't help, why bother. Besides, it is a
procedure that is fairly easy to botch.