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A question for audio geriatrics - developing magnetic audio tape

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Alex Rinquest
A question for audio geriatrics - developing magnetic audio tape
on Feb 10, 2006 at 12:07:05 pm


In the old days of radio broadcasting when we used material from various and questinable sources, audio correspondants often would use their domestic 4-track machine to record their contributions. Likewise being on the move their head azimuth would often go out of alignment resulting in having to plead with engineers to do their best to resusticate such material.

Their was an American product which usd to provide a few glass slides, cotton buds, alcohol and a 'developing fluid'. What one would do is immerse a portion of the tape in the liquid and then view the resulting 'developed' tape under a magnifying glass where you could view how the head alignment looked for that particular audio section.

Obviously there was more to it than just that but these boffins saved many a valuable contribution from being rejected outright or being eq to the point of telephone quality.

Does anyone out there have any idea what this chemical could have been.

I am sitting with piles of 4 track tapes, crosstalk for Africa and would welcome a little chemical assitance when the audio drifts in and out of alignment.

It's a long shot but someone somewhere may just have a clue. The ad on the box was typical of it's time...male holding up developed tape and wife (in background) smiling like my man the genius.

Alex Rinquest


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David Jones
Re: A question for audio geriatrics - developing magnetic audio tape
on Feb 10, 2006 at 11:37:01 pm

My Thoughts.... Vist your neighborhood pawn shop and purchase a used 4-track dirt cheap.


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Bag
Re: A question for audio geriatrics - developing magnetic audio tape
by
on Feb 11, 2006 at 1:40:36 am

I'd try and query someone like the BBC or any of the long-established studios who might have done some work in restoring old recordings.

Graeme.


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John Fishback
Re: A question for audio geriatrics - developing magnetic audio tape
on Feb 12, 2006 at 10:32:45 pm

Geriatric? Not quite yet. However, I do admit to knowing how to edit with a razor blade.

Here's a manual approach that might solve your problem. The azimuth of the playback head has an adjustment screw. If you turn it one way or the other whilst listening to playback, you can move the head into a position to obtain the best sound. After you finish with this, you should return the head to its spec posistion. You can do that by finding an audio alignment tape. These should still be available on ebay or perhaps a local broadcaster would have one. You play the tape and adjust the azimuth control until you get maximum output.

Hope this helps.

John

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Ty Ford
Re: A question for audio geriatrics - developing magnetic audio tape
on Feb 13, 2006 at 3:04:45 am

First of all Alex,

Bite me, for making agistic smart remarks. :)

Second of all, yes there was something called Magna See or Flux see. An emulsion in which small magnetic particles were suspended.

When "painted" on the oxide side of tape, visible patterns that indicated the tracks. I haven't seen any in years.

OTOH, if it's just 4-track tapes, what's the big deal?

Regards,

Ty Ford

Ty Ford's "Audio Bootcamp Field Guide" was written for video people who want better audio. Find out more at http://www.tyford.com


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Dubbing Mixer
Re: A question for audio geriatrics - developing magnetic audio tape
on Feb 19, 2006 at 9:57:10 pm

Hi, Ex BBC guy here. We used to use something called "Edivue Diluent" to 'read' magnetic tape. It was a suspension of very fine iron filings in a volatile solvent, made, I think by Ampex for manual(!) VT editing. We also had 'pelicles'. Again, iron filings suspended in solvant behind a very thin membrane. Both allowed you to 'develop' the magnetic image on the tape. But, to be honest, for your purposes, you'd be better off tweaking azimuth by ear.



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Will Salley
Re: A question for audio geriatrics - developing magnetic audio tape
on Feb 27, 2006 at 1:24:18 am

You need to determine what type of 4-track machine the tapes were recorded on - consumer models, and some later pro models recorded quarter-track in both directions resulting in a stereo program. Pro models recorded quarter-track in ONE direction and resulted in 4 mono or two stereo tracks. The difference is the stereo tracks on the pro models were on the first and second tracks across the tape, whereas the consumer models put them on the first and third tracks. This was done to make the pro model compatible with half-track machines - the standard for broadcast 1/4" at the time. However, your problem sounds like either burn-through (oversaturated signal adversely affecting the adjacent layer), accidental partial erasure or stretched tape (common if magnetic oxide tape is left out of the box and exposed to a heat source).


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