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This dovetails with what I said on two fronts:

1. you can't just assume that you can bake a tape many times and it will playback just fine each 
time. That's not been my experience. No one has done quantitative research into what happens to the 
tape surface or the order of the magnetic particles from baking. I assume something goes on that 
adds "fuzz" and "dullness" to the sound, some physical process related to baking and cooling and 
sticky-shed itself.

2. tapes DO wear out from too many playbacks. I've had this happen with different kinds of tapes in 
my personal collection. Cassettes eventually develop a loss of level and dullness, and they don't 
track Dolby correctly, especially Dolby C. Reels get dulled down and peak levels drop off somewhat. 
I assume that the oxide surface literally gets worn down each time it plays and obviously some oxide 
is always coming off or we wouldn't need to clean heads and guides. I also think there's low-level 
magnetism issues going on, not exactly sure where or how, but it's some sort of slow low-level 
erasure mechanism.

Jeff, what did the mastering engineer eventually do? Did you have safeties in the vaults?

In a modern context, copy tapes CAN be used to make great-sounding modern reissues. Listen 
particularly to the Copland 3rd mono (Dorati/Minneapolis) in MLP Box 3. That was a BADLY MADE dub, 
unusable until modern times. It was all that was in the vault. Aside from a poor-sounding sonic 
spectrum as played with no expert mastering touch-up, it was full of wow and flutter. We used 
Plangent Process to transfer and fix the time-domain problems. First of all, the wow and flutter was 
fixed. Second, the smearing effects of the dub generation were eliminated, so instruments were in a 
specific place and there was a surprising depth of field for a 1953 mono recording. The 
sound-picture stabilized and the dynamics lit right up. With expert mastering EQ nip and tuck by 
Andy Walter at Abbey Road, we got a really nice result. My point is, you can use dub tapes and get 
good results, and sometimes it doesn't even take that much work. The caveat is, you need to use 
modern methods and processes to get the good results.

-- Tom Fine

----- Original Message ----- 
From: "Jeff Willens" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, April 08, 2015 1:06 AM
Subject: Re: [ARSCLIST] More tales of woe from the tape vaults


> Worn out tapes are absolutely in the vaults right now, and have been for
> some time. I've come to find out (and perhaps others can correct me), that
> there is a finite number of hours a polyester-backed tape may be baked
> cumulatively before it stops working on the binder and/or it stops giving
> the fidelity it used to offer.
>
> As for tapes in record company vaults, having worked at more than one major
> label, I can say that you just don't know who's been on a tape before you
> get hold of it. Some engineer may have tried to play a shedding Ampex 456
> tape for a transfer without baking it, and lost a ton of oxide in the
> process years before you. If so, there went your high end, and all your detail.
>
> I had to do tape transfers of a very prominent 70s R&B band (who will remain
> nameless) for an outside mastering engineer doing a CD compilation. They HAD
> to be from the "original masters". All the masters were on Ampex 456 and 406
> 1/4". All had been baked and used scores of times over the years. I checked
> and baked the tapes for our usual amount of time, set up my machines, did
> the azimuth, etc. All was set to go. I put up the tapes. And they sounded
> like crap. Every last one of them. I double checked my entire set up. I
> checked the tape path. I had other engineers checking everything. Nothing
> made sense. All the tapes sounded like I was playing them from the outside
> -- muffled, muddy, and smeared. Still, I transferred them flat and sent them
> on.
>
> 2 days later, an extremely irate mastering engineer called me up and
> demanded to know why I transferred the tapes inside out. When I explained
> what happened, he couldn't believe the tapes could just "wear out" like
> that. But that is what happened. They were utterly shot. No amount of
> baking, EQ, azimuth tweaking, or sonic wizardry at the time was going to
> bring these things back from the dead. The ME used other sources.
>
> So it's not necessarily "shelf life" that contributes to a reel of tape's
> demise, but the use and handling it may get over the years that does the
> ultimate damage. And that damage can be irreparable.
>
>
>
>
>
> On Tue, 7 Apr 2015 19:06:13 -0400, Robin Hendrickson
> <[log in to unmask]> wrote:
>
>>I had a conversation once with someone who worked in the
>>Capitol/EMI/Universal system, and this person told me that the "the
>>old tapes are wearing out" and that all tape has a maximum shelf life
>>of 30 – 40 years.
>>
>>That sounded like BS to me; I know there are older tapes out there
>>that still work fine. (No guarantees, of course.)
>>
>>This Tom Petty story made me wonder whether there is some fallacious
>>conventional wisdom out there that would lead one to rush to a verdict
>>of "Yep, no way these old tapes are gonna work, we have to use
>>something else."
>>
>>The mind reels. Excuse the pun, this is a serious matter indeed.
>>
>>Robin
>>
>>
>>
>>On Tue, Apr 7, 2015 at 5:26 PM, Richard L. Hess
>><[log in to unmask]> wrote:
>>> On 2015-04-07 3:18 PM, Eric Jacobs wrote:
>>>>
>>>> 2-inch tapes with sticky shed may not respond as well to baking as
>>>> 1/4-inch.
>>>>
>>> That is true in the sense of in the same or similar time frame.
>>>
>>> I don't think there are precise formulae for predicting the time either to
>>> achieve thermal equilibrium or to achieve moisture equilibrium in a tape
>>> pack. Vos (1994) inspired me to develop a rule of thumb that moisture
>>> equilibrium appears to take 1500 times as long as thermal equilibrium in a
>>> one-inch tape, based on my extrapolations from his curves.
>>>
>>> We have long suspected that the width of the tape was a large modifier of
>>> this ratio. I based my estaimate on Vos's graphs which seemed to indicate
>>> that a 1-inch tape pack, might achieve thermal equilibrium might in 100-200
>>> minutes while it might take 100-200 DAYS to achieve moisture equilibrium. I
>>> felt that a factor of 1440 implied far too much precision in the
>>> calculation, so I rounded it to 1500.
>>>
>>> Further pointing to this is what Stuart Rohre has reported on the Ampex
>>> mailing list and elsewhere. He has been responsible for retrieving the most
>>> information possible from some 1-inch instrumentation tapes which are
>>> 15-inch diameter tape packs on glass precision Corning reels with no
>>> windows. The windowless reels further slow moisture diffusion. He had
>>> originally said they were baking for several days and could get through
>>> about half the tape and then had to rebake, but they also had to run the
>>> tape through their Bow tape cleaners. Partially at my suggestion and
>>> partially on his own initiative, Stuart found that if he baked the tapes for
>>> 30 days, they would play through without the need for any tape cleaning or
>>> re-baking and he was getting very clean signals off the tapes at that point.
>>>
>>> So, are the two-inch tapes not responding to baking or simply in need of
>>> more of it?
>>>
>>> One 7-inch reel of 1/4-inch tape that had been exposed to high humidity
>>> cycles overnight had a very easy-to-remove mag coat when first inspected.
>>> When it was stored in my air-conditioned home (minus the economizer cycle
>>> bringing in Los Angele's famed "Marine Layer" of "night and morning low
>>> clouds") for 3-4 months, the same test that initially showed mag coat
>>> removal could not be duplicated and the tape binder seemed very secure at
>>> that point.
>>>
>>> The "more baking" concept pertains to tapes like Ampex 456, 406, and 407 as
>>> well as the instrumentation tapes made by Ampex at about the same time. It
>>> may also apply to Scotch 226 and 227 and possibly Scotch 250. It probably
>>> does not apply to Agfa tapes which have some of their own nastiness.
>>>
>>> This web page attempts to categorize tapes by degradation modality, and
>>> degradation modalities are currently described more by what can ameliorate
>>> their effect than by the actual chemical/mechanical failure modes. My
>>> decade-long goal of a "pool-test kit" for tape degradation measurement is
>>> farther in the distance than it was when I started the quest.
>>>
>>>
> http://richardhess.com/notes/formats/magnetic-media/magnetic-tapes/analog-audio/degrading-tapes/
>>>
>>>
>>> Cheers,
>>>
>>> Richard
>>> --
>>> Richard L. Hess                   email: [log in to unmask]
>>> Aurora, Ontario, Canada                             647 479 2800
>>> http://www.richardhess.com/tape/contact.htm
>>> Quality tape transfers -- even from hard-to-play tapes.
>>========================================================================
>
>