Path: utzoo!attcan!uunet!dino!ux1.cso.uiuc.edu!uwm.edu!csd4.csd.uwm.edu!info-high-audio-request
From: bilver!bill@uunet.UU.NET (Bill Vermillion)
Newsgroups: rec.audio.high-end
Subject: Re: Tape Squeals
Message-ID: <7059@uwm.edu>
Date: 18 Oct 90 13:04:14 GMT
Sender: news@uwm.edu
Lines: 64
Approved: tjk@csd4.csd.uwm.edu


In article <6998@uwm.edu> cbp@foster.avid.oz.au (Cameron Paine) writes:
>In <6869@uwm.edu> JFARRINGTON@EAGLE.WESLEYAN.EDU (Jim Farrington) writes:
>
>>In reply to Steve Graham's squealing reels, I think I can throw some light
>>on the subject (though you may not like the answer).  [...]
>
>Following this topic has made me feel slightly ill... We have ~500 hours
>of seminal local music which was recorded onto (predominantly) Ampex tape
>between 1979 and 1985. I have banned playing these tapes until I find a
>way of extracting the material and this thread has provided the first
>concrete information I've encountered. I had developed a different theory
>and I'll mention it briefly because I think it has some merit. Note, I'm
>not arguing the point with Jim. 
>
Tape doesn't rely on air as a lubricant.  The lubricant is built into the
oxide.   There have been major problems in the last few years with oxide
formulations as suppliers to the manufacturers sometimes change chemical
composition of certain supplies, which affect other things along the way.

We had a problem with this with a bunch of Ampex tape (2" Grand Master)
several years ago, and the oxide would become gummy.

Another problem surfaced on Scotch whereby the carbon impregenated backing
would adhere to the oxide and would then be stuck to the heads.  Sometimes
the would occur within a minute of playing.

A friend of mine lost the master mixes of the "Blackfoot Live" recorded in
London.  When the tape was finished playing enough of the oxide had come
off that the tape was junked.  The only good part of this was the failure
occured during the transfer to PCM digital, so the mix is still available.

This has become a major problem.  So much so that Agfa has researched it
thoroughly and has developed a process to re-lubricate the tape enough so
that a transfer can be made onto better media.   I understand it involves
coating the tape and baking it.  It is a laboratory procedure, and I
understand they do it in LA, but not sure if done anywhere else.  That
would be the last resort but it won't be cheap.

I have seen tape disintegrate in various way.  I have seen oxide flake off
the tape.  This occurs when the oxide and the backing material and the
oxide shrink or dry out at differing rates.  More typical with acetate than
mylar based media.

Splices are another killer.  No one seems to have perfected a splicing tape
that works right.  I have had some that bleed in a matter of months. Others
that completely dry out. 

You mention that repacking the tape about 10 times or more helps.  But I
suspect it is not the air, but moisture from the air helping to relubricate
the tape.  You don't want air between the tape and the head, you want
intimate contact.   I have had moderate success with holding the tape
between the folds of a record cleaning cloth.  But I don't know if they
make those anymore.  These were the cleaning cloths with silicone
impregnated in them.

Best of luck.  You will need it.

bill


-- 
Bill Vermillion - UUCP: uunet!tarpit!bilver!bill
                      : bill@bilver.UUCP