Radio 3: pre-echo on Liszt loud piano parts

[Tim Gillett]

Thanks forumuser840717, it was Roger Nichols July 2006 article

As everyone knows by now, analogue tape suffers from 'sticky shed syndrome'. The tape companies suggested baking the tapes to enable playback temporarily. In 1992 I started using a vacuum process to recover these tapes; I enlisted one of the original scientists who developed Mylar and the oxide binders for DuPont to help develop it. It works perfectly and turns out to be permanent. Tapes processed in 1992 still play back perfectly today, without the increase in distortion as a result of baking.

Thanks for the Roger Nicholls quote, MOF and 840717. I can understand how vacuum would eventually remove the moisture from the tape, but I dont understand how this seemingly harmless vacuum process would also change the tape so that it no longer reabsorbed moisture.

[ef37a]

He recorded the complete piano works twice: once in the 60s (ADD), and then again in the 80s (DDD).
Now, guess which recordings have the digital distortion?

For a 60s recording it would have to be AAD.
Have you ripped the 80s recording into your computer to see the waveforms? It just might be the CD player distorting if the mastering took the peaks to extremely close to 0dbFS.

Yes, many years ago son and I burned CDs to play on a Philips CD480 (still got it) using Nero which by default normalized to 0dBfs and the machine would produce distortion on peaks. Played on the optical drive on the desktop, no problem. We found a way to stop normalization and burn a dB or so lower.

Dave.

[Hugh Robjohns]

I can understand how vacuum would eventually remove the moisture from the tape, but I dont understand how this seemingly harmless vacuum process would also change the tape so that it no longer reabsorbed moisture.

Nor me... there must be more to it...

I found this patent that describes a process which strips away the backing and claims to be a permanent fix.

And there's a discussion on a vacuum dessication process here.....

I'm sure there's more to be found on t'internet but I need to go out now so will continue the research later.

[MOF]

I dont understand how this seemingly harmless vacuum process would also change the tape so that it no longer reabsorbed moisture.

The hydrolysis was caused by a change in the binder chemistry. As I understood it a chemical was added to change that binder’s propensity to absorb moisture.
Tapes before 1985@ didn’t hydrolyse, I read that the EMI tapes that were used at Abbey Road in the 1950-60s used a binder derived from Whales blubber.

[James Perrett]

Tapes before 1985@ didn’t hydrolyse, I read that the EMI tapes that were used at Abbey Road in the 1950-60s used a binder derived from Whales blubber.

You're around ten years out - 1975 seems to be the changeover date. Certainly plenty of late 70's Ampex tapes require baking. The legend that I've heard said that Ampex used whale products up until the mid 70's. Certainly, from a UK perspective, Ampex tapes are the main brand to exhibit the hydrolysis problem - the only others that I've encountered were some later 3M tapes which I think were made in the US.

I wonder if there was a difference between European and US production processes which made this hydrolysis more prevalent in US made products? I also find that I have more issues with tapes from US archives - I don't know what they do over there, but US stored tapes are often a nightmare to transfer whereas tapes that have lived all their lives in the UK give far fewer problems.

[MOF]

You're around ten years out - 1975 seems to be the changeover date. Certainly plenty of late 70's Ampex tapes require baking. The legend that I've heard said that Ampex used whale products up until the mid 70's. Certainly, from a UK perspective, Ampex tapes are the main brand to exhibit the hydrolysis problem - the only others that I've encountered were some later 3M tapes which I think were made in the US.

I had 1985 in my head but I think you’re right as a year or two ago I laced up an old 4 track tape on my TEAC (bought in 1978) and it exhibited the classic signs of ‘sticky tape’.
I don’t think all tape manufacturers used the same binder as Ampex.