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Re: [ARSCLIST] Re print-thru - tails out
Over 20 years ago at a convention I had an Agfa engineer explain why
European tapes wind more evenly, and it didn't have to do with the
coatings. It had to do with the base. The plastic was tensilized in
the direction of tape movement. Remember, the AEG Magnetophons from the
mid 30s thru the mid-40s did not use reels, only an aluminum bottom
plate. This idea is also evident on the first Ampex, the 200. Once
they started to use American tapes they had to go to reels on the 300.
The post war Telefunkens, Studers, and other European machines largely
stuck with pancakes because they could.
Many years ago I read a study on print thru which stated that most of
the eventual print thru occurs in the first two days after recording,
and that it can be accelerated if the tape is hot and if it is subjected
to a magnetic field that is too weak to erase it but enough to get the
magnetic fields active. (I once noticed enormous print thru on the
linear audio tracks of a videotape that someone had tried to bulk erase
with a hand-held eraser that was not strong enough to do a job on wider
tapes, and they had not done both the top and bottom of the cassette.
But it was enough to set up magnetic flux that recorded layers onto the
adjacent ones) It also displays different remnance properties than
biased recordings in that it can be reduced by physical flexing of the
tape. Hence the earlier stated suggestion of winding the tape before
playing. If the tape is left tails out, you have to wind it back. But
the suggestion was that a complex tape path that flexes the tape in both
directions back and forth is a more efficient erasure method. Those
machines with several rollers will do nicely, but there also was
discussion of the degree of flexing, so it might have been better if the
rollers were smaller in diameter (but I don't remember). It might also
help if we would put a twist in the tape when threading for winding.
For some reason, print thru is stronger from the inner layer to the one
above it. That's why a heads-out tape has pre-echo. I assume that the
magnetism is moving thru the base to the oxide touching it. If we used
B-wind like the original AEG Magnetophons and the Ampex 200, I suppose
that print-thru on a heads-out tape would be pre-echo. Was this an
accident or were the Germans on to something? (For the non-historians
here, B-wind is oxide out, A-wind is oxide in. You might see mention of
this if you have tape boxes or catalogs reaching back into the 40s or
David Breneman wrote:
--- On Thu, 4/2/09, Goran Finnberg <mastering@xxxxxxxxx> wrote:
If the tape has country laning due to bad slitting,
Ampex/Scotch, then the actual tape pack is much worse than
tape, AGFA/BASF, which do not exhibit country laning using
slitting machines because of the use of AEG hubs by the
Germans on their
tape recorders with no top flange and thus using American
instant disaster on such equipped tape machines.
I've been told by at least one person who worked at
Ampex that one of the reasons that German made tapes
don't "ride up" on the tape pack (and therefore don't
require a top reel flange) is that the oxide side isn't
as highly polished as is common with American brands.
The rougher surface traps less air, so the wrap settles
down immediately without floating above the previous
wrap. It's that floating that is the major cause of
tape not packing evenly on fast wind. I'm no expert
on this, just passing on something that is taken as
common knowledge in some circles.