Re: [AV Media Matters] Re-Evaluating Tape Mastering Stock

[rohre@ARLUT.UTEXAS.EDU]

Print through is an interesting effect.  I have heard examples in
voice audio tapes 30 plus years ago, and believe that was on 1.5 mil
tape.

Yet, my more recent tape work has been with one mil and half mil
tape materials, and with low frequency ocean noise, at saturation
level recording, we do not see print through effects.

Jim Wheeler pointed out that good back coating, to maintain flat
packing, has edges of carbon that stick upright out of the backing
to hold the next strand. Perhaps this slight elevation increases the
spacing between strands, lessening contact magnetic printing.

Finn Jorgensen, in his book, "The Complete Handbook of Magnetic
Recording", points out that the maximum print through occurs when
the wavelength of the recorded signal is approximately equal to the
total tape thickness.  Print through results from smaller magnetic
particles that are unstable and thus easily affected from the field
in the next strand layer.

A technique for reducing print through effects was to pass a small
dc or ac current throught the RECORD head during playback.  This
would erase the unstable particles without affecting the recorded
data.

Print through is most severe at 1500 Hz on 2 mil tape where the ear
is most sensitive to the frequency, thus the voice print through
effects have been the most noticed over the years.

Stuart Rohre
UTx ARL Recording Lab

Moderators Comment:
How about coercivity? I would have thought that the newer higher coercivity
tapes would have a lower level of print through almost regardless of tape
thickness (at least relative to the higher energies) because the energy
needed to print through would be much higher then that available to cause a
state change. Older tapes with low coercivity I can understand - but it
would seem to me that the energy required to transfer at the higher energies
would just not be "available". That was one thing  I was thinking in asking
the question. I.e. if the base films now are much better in terms of stretch
and stability - and there is probably consensus in that regard - then is
there really any reason NOT to use 1.0 mil? I can't really think of any
other then "this is what everyone has been doing for a long time" (me
included) and that isn't really a great reason.

BTW I really wanted to comment on the EXCELLENT quality of the feedback on
this thread and many others - thank all of you so much! There is a very
impressive level of expertise available here.

jim