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Re: [ARSCLIST] Ampex 456 and Shamrock 041 Manufacturing Specs?
I dunno, Mike. Sticky-shed high-grade tapes are a pain but if you bake them you can recover what's
on them and they will play correctly and were capable of making excellent recordings when new.
Meanwhile, an ill-slit country-laning junky castoff instrumentation tape never recorded audio
properly and will never play properly. It was folly from day 1, like recording music on
dictation-grade cassettes or, conversely, thinking you're being "pro quality" and using high-bias
CRO2 cassettes in a junky little interview recorder designed for normal bias tapes in lightweight
In the end, we all get on the receiving end of someone's thrill because ALL magnetic media will wear
out eventually. That said, I feel very lucky to have dodged a sticky-shed nightmare, having only
bought 20 reels of Ampex backcoated tape in my youth. Everything else (hundreds of reels) was on
Scotch 206/207 and Maxell UD, all of which so far still run well.
-- Tom Fine
----- Original Message -----
From: "Michael Biel" <mbiel@xxxxxxxxx>
Sent: Sunday, February 22, 2009 5:27 PM
Subject: Re: [ARSCLIST] Ampex 456 and Shamrock 041 Manufacturing Specs?
Tom Fine wrote:
3M also had cheapo "Highlander" brand tape for a while. I'm not sure if that was stuff that
didn't meet spec or if it was 3M's last generation of brown-oxide, no-backcoat duplicator grade
My experience with olden days Shamrock (brown-oxide acetate and early polyester days) is that
it's not destruction-prone like some tape of that vintage but it usually country-lanes all over
the place . . . Just what did a batch of tape have to do to get badged Shamrock instead of
I have no answers, only a bunch of urban legends.
1) The tape might have been the outside slits from the original 18-inch wide rolls -- that the
regular grade tapes were the ones in the center. That might mean the oxide was full grade but
they didn't trust the slitting. Or maybe the oxide might be thinner towards the edges.
2) These were the short ends of the rolls and are made from two shorter parts spliced together.
I remember that some tapes seemed to have a splice about 2/3s of the way into the reel. Remember
that most full-grade boxes mentioned that they are "splice-free". The tape might be fine but
might change specs at the splice!
3) The slitting might have been bad. I have one reel I bought in1965 that is slightly too narrow.
In 1967 one of the prolific producers at our station bought three or four reels that were
slightly too wide and wouldn't play on the two home-grade Ampex machines in our main air studio.
The tapes would just stop dead because these had the self-thread guides the full width of the tape
slot. Unfortunatly, before we discovered this, he was assembling dozens of shows from things done
on different reels of tape, so a segment on almost any of his shows might have come from those
wide reels. For the rest of the year we had to run any of his shows from a machine in one of our
other studios and patch it into the air studio board.
4) These were computer tapes that didn't make the specs for computer tapes but would be just fine
for audio when they slit them down from 1/2-inch. This was the rumor especially when the highly
polished oxides started appearing. Of course computer tapes needed different bias levels than
audio machines and were designed for different wavelengths than audio. Then came the rumors these
could be slit videotape. That would be even worse since the oxide particles might have been
optimized for the different azimuith angles.
5) The black oxide backcoated tapes were 456 that didn't meet specs but were still better than
regular grade tape. Oy veh.
6) The graphite lubricated backcoated tapes didn't meet the grade for tapes for cartridges. THIS,
I believe. Whenever I got a reel of this, I set it aside to rewind carts. I don't think this
stuff wore well.
Why oh why oh why did we buy this crap?? Because we were starving students or poorly paid
professors, etc. And now we get that vicarious thrill knowing that those who could afford the
GOOD stuff are having the same or worse problems now that we have with the crap!!!!
Mike Biel mbiel@xxxxxxxxx