GUBBINS@RADC-TOPS20.ARPA (Gern) (03/15/85)
The logic behind Bulking (Degauss) computer floppy disks, computer magtape,
and especially audio tapes is that the normal erase mechanism of the
device (note that floppies don't erase, they just plow over) never does
a perfect erase. In audio, this will record the new music over a slight
hiss and possibly some remains of the old music which can sometimes be
heard at high volume in between songs.
A good bulk erase of the media (ie. heavy nuke as they usually do) cleans
off all signals: Normal recordings, stray signals, any trash between
tracks (audio and computer between tracks that normally can't be reached
by the normal mechanism). Degaussing (bulking) the media basically
scrambles the magnetic fields of the media back into its original random
form. This is the best way to remove any recorded spikes (that error
that reformatting the disk won't remove, but if you bulk it, then format,
it disappears). Spikes are too large (wide) to erase normally. Remember:
especially in audio tapes, that the erase head can't be powerful enough
to stray over and erase adjacent tracks (the other side of the cassette).
Good policy is to always degauss the media before reusing it, be it
audio or computer. Computer magtapes require an oven-like degausser
to spin them in a harsh magnetic field in a shielded case (it can nuke
out your digital watch if you get too close).
I always bulk disks before reformating them and audio tapes before
re-recording, and harsh nuke Magtapes in the degausser before reuse.
I use and recommend (standard opinion disclaimer here, etc.) the Radio
Shack bulk tape eraser for cassette tapes and disks. It works well
and is only <$15. For video tape/cassettes, you need the bigger version
that they sell.
Bulking does not extend the life of the media (life is based on wear,
aging, dirt, scratches, etc.), but it does restore the magnetics
as best as possible (wear is the hinderence here) to its orginal form.
Audio (actually, I mean Audio, video and all other analog information)
media generally does not require any formating. Computer disks (not
magtape, 'cept for a header-tape-name-type record) generally require
formating after bulking, be it floppy, hard disks (packs, platters,
etc.). So before you go bulking it (DEC RX02, etc) you better have
a way to reformat it. Most all microcomputer operating systems ('cept
DEC in the early days) provide the user with a format utility.
If they don't (ripp off here), the media must be bought formatted at
the factory or done my field service.
Any questions will be entertained.
Cheers,
Gern
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