From: utzoo!decvax!harpo!seismo!rocheste!stevans
Newsgroups: net.audio
Title: Why it might not be good to demagnetize
Article-I.D.: rocheste.360
Posted: Mon Jan  3 01:54:07 1983
Received: Tue Jan  4 01:31:54 1983

No, I do demagnetize my tape recorder heads, about once a month.

The exact reason I think it may not be necessary or desirable
is as follows:

   A completely demagnetized head is not demagnetized relative to the
   tapes recorded and played in the deck.  A truly demagnetized head
   is at "zero" magnetic level, while the average magnetic level of
   the recorded tapes is the nonzero bias.  As you play and record
   tapes, the magnetic field of a head will asymptotically assume
   that of the bias level.  The truly demagnetized head will thus erase
   more of the recorded information than the one which has adjusted itself
   to the bias level, since the average difference between the demagnetized
   head and the tape is greater than the average difference between
   the bias level head and the tape.

   In time, the head will always adjust itself to the bias level of the
   tapes, erasing them less, but producing more noise on playback.  I am
   not sure of how much more noise, but I don't believe it is more than
   a few dB.  Though I don't like noise, I would rather hear it more
   and erase my tapes less.

Can anyone explain why I might be wrong in these theories?

          Mark Stevans, U of Rochester, NY
          (seismo or allegra or brl-bmd)!rochester!stevans