The Mudcat Café TM
Thread #57471   Message #904436
Posted By: Bob Bolton
05-Mar-03 - 09:50 PM
Thread Name: Sound archives decaying
Subject: RE: Sound archives decaying
G'day again Steve (et al),

Yout paragraph:

Magnetic audio tape even as little as thirty years old can go soft as the binder oozes out of the base. Even when the tape doesn't break, the binder can stick the turns together on the reel and gum up the tape machine ... solution is to bake the tape ... tape can only be played once ...

does need a quick explanation.

This is not a general problem of all old tapes, but a specific problem with "high quality" (studio mastering, &c), usually the larger reels (7" or 10") from a certain group of manufacturers who went over to a 'great new tape substrate' that delivered the flexibilty needed for the new (stand-alone) video recording suites along with improved lubricating properties. Unfortunately ... it turned out that they hydrolised badly in a few years (or a few weeks, in New Guinea!)

It took a while before the problem was noticed ... and even longer before the manufacturer admitted that there was a problem. The tapes I refer to above were recorded 6 or 7 years after the new formula was introduced ... and by that time some alarm bells were ringing, but nobody was putting out the fire!

Anyway, older tapes ... and newer tapes ... are much more stable. Cheaper tapes that didn't opt for the new formula are (relatively) fine. The basic risk area for this particular problem is any studio or professional recordings from (~) the mid '70s to the late '80s. Someone working in the recording industry in the following decades, could probably refine this warning considerably.

vectis and Dale: On the complete speed switch adjustment: I haven't needed to do this one, decreasing speed by 50% and lowering pitch, (although I once had to do the equivalent by re-copying and speed-shifting to get a 3¾ ips dub of a collector's field recording out on a radio programme - where everything ran at 7½ ips or 15 ips), however I have made a (~) 30% slowdown of a waltz track ... retaining pitch ... to adapt a brisk waltz for a more stately style. Fortunately, the playing stood up to the increased scrutiny!

I must suspect that such an extreme change could restrict your high frequencies to only 10 KHz ... but your 4.75 cm / 1 7/8" per second tapes have probably already done that!


Bob Bolton