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