[AV Media Matters] Print-through

[Jim Wheeler <Jimwheeler@aol.com>]

The expert on the subject of print-through is Neal Bertram.  Neal
was a Research Physicist at Ampex and published a 33 page article
about print-through in the October 1980 issue of The Journal of the
Audio Engineering Society.  Neal is now the Head of the Center for
Magnetic Recording Research at U.C. San Diego.

Print-through is caused by "thermal idiots"--magnetic particles that
didn't line up when told to by the field of the recording head.
Thermal idiots are weak particles so they can have their magnetic
dipole orientation changed easily.  One of the Studor machines
applies a magnetic field that is too weak to erase the good guys but
powerful enough to neutralize the problem dipoles. I never liked the
idea of a magnetic field near a master tape.

Neal and his research colleges discovered that thermal idiots can be
returned to their random orientation by a mechanical shock.  I joked
that you should drop the reel of tape on a concrete floor but Neal
didn't like that approach. He found that a couple of high-speed
passes through a tape recorder would greatly reduce the
print-through.  You should use a machine that has several turns in
the tape path to stress the tape.  I doubt that an ATR-100 would be
of any use since it has such gentle tape-handling.

Jim Wheeler