A New Year’s view of at-risk audio formats

This article was first written in January 2015, with minor revisions in 2018. The revisions made in 2024 are highlighted, like this line. The deletions are struck through.

There are many factors that affect the ability of people like us to digitize tapes for you, our clients.

One of the most difficult issues to balance is the physical space that different formats take up, the ongoing maintenance of these formats, and, to be brutally honest, their return on investment.

What we discovered is that some of the machines we were archiving for future use would not work when they were brought out of storage. Rubber parts, capacitors, and lubrication are probably the most prevalent causes of failure. We have said to clients more than once (with a wry smile), “Yes we can probably restore your tape, but first we need to restore a machine.”

Manufacturer and maintenance depot support for various formats is waning or fully discontinued. Parts are hard to come by, and good machinists with an interest in doing this are either non-existent or very expensive.

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MD5 Checksums bring peace of mind

If you ever worry about a bit error happening to your files and not finding out about it, you should use MD5 checksums (or some similar method) to be able to verify that the file has not changed.

The general theory behind a checksum (or “Message Digest” = “MD”) is that it provides a unique 128-bit number for each and every file, based on its content. If one bit changes, the MD5 checksum (sometimes called “hash”) changes. The checksum is repeatable, does not permit discovery of two different files that produce the same checksum, and is non-reversible (i.e. you can’t create the content from the checksum).

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Phantom powering of early proprietary- and T-powered Sennheiser mics

I finally figured out how to power the Sennheiser MKH-104, 404, and 804 from 48 V phantom power (P48) which is very common on professional and many prosumer mixers and recorders. The MKH-X04 series requires -8V for operation. Please note that some portable recorders do not generate P48 even on their XLR connectors. This will not work with P12 or P24 inputs. It works like a charm on P48 inputs (at least from Mackie, Yamaha, and Sound Devices). Thanks to everyone for their input and assistance. 

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Studer A80RC mod for either tension sensor stop

The Studer A80RC as designed stops only when both tension sensors lose tension. When using fragile archival tapes, especially at slower speeds, this creates some difficulties as the tape end weaves through the head block. Here is a modification which makes the A80RC operate like an A810, stopping the tape when either tension sensor looses tension. The mod is completely done on the 1.081.393 Command Receiver board and involves adding two parts and removing one.

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Success with squealing Shamrock 031 tape

I spent days trying to get Shamrock 031 to play without much success. Since this is an Ampex factory budget brand (probably non-spec premium tape) I thought that it might be suffering from Sticky Shed Syndrome. I baked it for 12 hours and it still squealed. I then tried my usually successful cold playing technique and it still squealed. Cold playing has worked successfully with 3M 175 and Sony PR-150.

I was getting rather frustrated and since it was a four-track tape and one of the techniques that is supposed to reduce squeal is to play the tape faster, I dragged out my Racal Store 4DS instrumentation recorder which has a 75,000 Hz bandwidth at 15 in/s and played it at 15 in/s and digitized it at 88,200 samples per second. After slowing it down 4x and ending up with a 10 kHz bandwidth (which I subsequently truncated to 5 kHz since there was no useful information above that, but lots of noise–same as the non-squealing portion of the real-time transfers on a Studer A810).

 Racal Store 4DS playing formerly squealing Shamrock tape

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Seeing the tracks II — An improved magnetic viewing system

I first wrote about seeing the tracks here in March of 2006. While these solutions work, the Plastiform viewer needs to be kept in a humidor and the Kyread spray is a bit of mess to use and the results are variable. One result of the Kyread treatment can be seen here (please wait for the pictures to load, it’s a big page).

Here is what appears to be a vastly improved solution:

Closeup of the viewer

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Soft Binder Syndrome and Sticky Shed Syndrome

For a current list of degrading analog tapes, click here.

For several years, we have been discussing the differences between Sticky Shed Syndrome (SSS) and Loss of Lubricant (LoL). It appears from my latest research (presented at the 2006 Audio Engineering Society’s 121st Convention in San Francisco in October) that LoL does not really factor into the equation for most tapes and that an overarching failure mode is Soft Binder Syndrome, or SBS. Sticky Shed Syndrome appears to be a subset of SBS.

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Securing the end of a tape to the reel

I receive many tapes that use very creative methods of securing the end of tapes to reels. Some don’t do it at all. Most 1/4-inch tapes are secured as shown below. Sadly, the superior Zebra tape is no longer available. This is the traditional crepe-paper type of tape sold for the application. The picture below should explain all.

Taping a tape to a reel

circa 1943 German acetate tape: anomaly or mine canary?

A few months ago, I transferred several Tonschreiber tapes which were IG Farben Magnetophonband Typ C manufactured in Germany prior to the end of 1943. These had been stored in their almost-sealed steel cans and stunk. The best description of the smell was old lemon chicken.

We know that the sealed can will accelerate the vinegar syndrome degradation. The big question is are these tapes an anomaly or the mine canary for some (or all) acetate tapes?

The composite photo below shows some of the conditions that we found. Note especially the rolled outer strands showing extreme shrinkage from vinegar syndrome.

Tonschreiber Tape

Click for a larger image.

We were able to transfer these tapes,   but the sound quality suffered due to the unsteadiness of the tape transport. The quality of the sound was due mostly to the fact that this was recorded at 30 in/s (probably 77 cm/s) with a full-track head. Nothing beats areal density for robustness.

Acetate tape buffered by cardboard box

I have been suggesting for many years that one of the reasons that acetate audio tapes have not suffered from vinegar syndrome to the extent that acetate films have suffered from this malady is because of differing storage practices. In general, film for many years was stored in sealed cans while tape has generally been stored in cardboard boxes.

I recently came across a 3-inch reel of acetate tape, not in its original box, that showed the following pattern in the box. This tape was recorded in Fall of 1964 and the photo was taken on October 2006, 42 years later. The tape played well, considering it was originally recorded at 1.88 (1-7/8) in/s.

Box discoloured by acetate breakdown products

All of the outgassed material that was absorbed by the cardboard was no longer free to degrade the tape.

Sticky Shed & Loss of Lubricant

This post has been updated as: https://richardhess.com/notes/2007/03/21/soft-binder-syndrome-and-sticky-shed-syndrome/

For a current list of degrading analog tapes, click here.

For several years, we have been discussing the differences between Sticky Shed Syndrome (SSS) and Loss of Lubricant (LoL).

Recent work in which I’m participating seems to indicate that what we thought was happening in both instances may not be really what is happening.

For now, the continued recommendation is to bake tapes for which baking works. These include:
Agfa (pre-1990): PEM 468, PEM 469
Ampex/Quantegy (1970s-1980s): 406, 407, 456, 457
Note: Recent reports indicate that these problems may exist in tapes  made in the 1990s
and later, even under the Quantegy name.
Audiotape/Capitol (early 1980s): Q15
Note: This tape may or may not respond to baking. Some tests will be conducted soon.
Scotch/3M: 226, 227, 806, 807, 808, 809

If these are squealing and leaving deposits, they should be baked (at your own risk). The Ampex patent for baking tapes can be found here.

The classic test for determining if a tape is suffering from LoL has been to bake it and see that baking fails. The assumption has then been that it is loss of lubricant. This test, however,  may exacerbate the condition and it is not recommended to bake suspected LoL tapes.

Tapes which appear to be suffering from LoL include:
Scotch/3M: 175 and Melody 169 (a seconds brand of Scotch)
Sony: PR-150
Pyral: (type numbers unknown for this French tape)

We have seen cassette tapes also suffering from LoL.

There are several ways to address playing LoL tapes, but, for the moment, we are not prepared to publish anything definitive beyond Marie O’Connell’s tried and true method shown here.

Let sleeping tapes lie—what to do with poorly wound tapes

Often a tape comes in for restoration that has been poorly wound or poorly stored. Here is an example:

cinched tape

One of the interesting things about this particular tape was it had been recently wound on a constant-tension professional machine prior to shipping to me.

We think that the entire tape had not been re-wound, allowing the higher tension wind to compress the inner core slightly, causing this cinching. After transferring the tape (which didn’t show much ill effect for its cinching), we still found it difficult to get the tape to wind smoothly on the reel.

Therefore, our current suggestion is if you find a tape like this, do not rewind it and attempt to clear up the cinching unless you are also ready to transfer the tape, as there are no guarantees that it can be wound better after unwinding.

Please see this post for an update (2008-02-15).

Project Notes: Advanced oxide delamination of a cassette

A client phoned me and said a cassette he was playing started to shed in his machine and he stopped and took it out. He sent it to me and as I pulled a little bit of clear leader out of the middle of the tape, this is what I found:

flaky_tape_01

Notice how the complete strips of oxide exist on their own, independent of the clear “leader” to which they previously were attached.

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Tape recorder bias frequencies

The discussion of what bias frequencies were used over time keeps recurring. Special thanks to Jay McKnight of Magnetic Reference Lab, Tom Fine, and Brian Roth  for input to this list. I posted this to the ARSC list, but wanted to include it here as well. This knowlege is useful for those who wish to archive the bias along with the audio for future application of time-base-error correction tools such as the Plangent Processes.

Bias frequences started low, apparently with 60 kHz for early consumer recorders, but Ampex started with 100 kHz. Other later machines used different bias and erase frequencies. We can see with a few exceptions, the top bias frequencies were commonly limited to 250 kHz for audio, with the Sony APR series and the Ampex ATR series in the 400 kHz region. For cassettes, a practical maximum appears to be about 150 kHz. Much higher frequencies (up to at least 8 MHz) were used in instrumentation recorders. An enumeration of several machines follows.

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Round-pin power cords for older equipment using PH-163 connector

The round-pin power cords used on older Hewlett-Packard and Dolby equipment  uses a connector called the PH-163. I think I have enough to last me. I bought my last batch in the early 2000s.

As of 2021 these cords are becoming more and more difficult to find…

Thanks once again to Rick Chinn, there is a source. These have European connectors, bare ends, or non-molded NEMA 5-15P plugs attached. Details below.

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U-Matic 3/4" Cassette Removal Procedure When Normal Ejection Is Not Possible — Guest Article

This is a guest article from Andreas Weisser who runs Restaumedia in Germany. Neither Andreas nor Richard can take responsibility for the work that you do based on these instructions which are provided on an as-is basis. Any risk of using them is solely your own and not Andreas’s, Richard’s, or anyone else other than you, the person undertaking to use these instructions. If you have any questions, please contact Andreas. — Richard

This is a step-by-step guide for the removal of U-matic Cassette from a Sony VP 7040/9000 U-matic Player by hand.

1 —  Turn the power OFF.

2 — Remove the Upper-Case of the video player. Use a Phillips screwdriver to loosen the fixing screws. Then pull the Upper-Case in the direction marked by the red arrows shown here in picture 1.

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Loading C-0 cassettes

One way of loading C-0 cassettes is to unscrew the shell and drop the old tape into the new shell.

I have found that reloading using a modified cassette machine is much faster and easier. The following images should explain the process:

Splice one end of the original tape into the C-0:

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Wet playing of reel tapes with Loss of Lubricant—A guest article by Marie O’Connell

This is the first of many guest articles here. Thanks to Marie for agreeing to share her wonderful work in playing tapes that did not respond to baking. SSS=Sticky Shed Syndrome, LoL = Loss of Lubricant
For a current list of degrading analog tapes, click here.–Richard

There has been a lot of interest in this issue recently and I’ve answered several people privately. Hopefully this location will make the work more accessible to all who are interested.

The general appearance of the Mark II. As you can see, I had the luxury of being surrounded by these great machines and so we sacrificed one with all the adaptations done by a great technician by the name of Noel McGinnity – we both agreed we still wanted it to look like an almost regular Studer! All the tubing has been adapted to withstand isopropyl alcohol and the IV drip bag does not leak.

I began working at Sound Archives/Nga Taonga Korero, which is a wholly owned subsidary of Radio New Zealand in 1994. My task was to preserve and digitize the entire NZ Composer’s collection to begin with. I was taught my skills “on the job” but was lucky enough to have the wisdom & know it all of several older broadcasting technicians at my fingertips.

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Binder adhesion to back of next layer

In several instances, we have seen binder adhesion to the back of next layer in the tape pack. When the tape is unwound, a portion of the the binder adheres to the layer it was resting on, and is pulled off the layer it was supposed to be on. It looks like this when held up to the light:

There are many possible causes for this adhesion (or pinning, as it is sometimes called). For this tape, we believe moisture intrusion and poor storage conditions contributed to the problem. It is often a problem with plastic leader tape.

Slow unwinding has reportedly helped, as has cold, dry storage for an extended period.

This tape   (Melody 169) also squealed, but we finally got an acceptable transfer. Fortunately, this was recorded on only one track, and it wasn’t the one with all the holes in this picture.

Rationalizing camera equipment — what do you need?

While the below was completed in about 2015, there have been more updates, the results are in abeyance as we shelter in place in April 2020. In 2019, son Robert, the musician, was bitten by the photography bug, so I started letting him borrow some of my equipment. He ended up doing nice wildlife photography with the 70-200 f/4 and 2x converter as well as some other lenses in our arsenal. I thought it was time for me to go much lighter. Somewhere along the line for some video work we ended up with a third body, a D7200, so Robert is using the two D7100s. I’m keeping the D7200 and the 16-85 lens. In order to go longer with less weight/bulk, I bought a 55-200 Nikon lens which is very compact and surprisingly sharp. Instead of fussing with teleconverters, I bought <gasp> a used Nikon 500 mm f/8 mirror lens — the final model which has a relatively close focus and is very compact. I have only done some preliminary testing and it might work for some things, but its compactness might be an offset for the doughnut out-of-focus highlights. In a sense, I’ve figured it’s time for Robert to explore the world of high-quality longer-lens photography and I can just play with it without burdening my wife’s and my travels.

The complete travel kit includes:

Wide angle: 24 mm equivalent on the D7200 at the wide end of 16-85 mm lens. To go wider, I have two choices: panorama or the 13 mm equivalent at 16MP on my Samsung S10+ phone. While I had a lot of fun with the 12-24 mm lens, it only goes to 18 mm equivalent, so going to 13 mm equivalent on the phone solves some problems if I don’t want to do a panorama. I have really been enjoying panoramas,  however. The phone also has an equivalent of 26 and 52 mm, both of those at 12MP. These options align with the small portion of my photography that has been done in this range: 3%.

Normal: 24-300 mm equivalent with the 16-85 mm and the 55-200 mm zooms. This covers 87% of my photography (see below). As a refresher, the “equivalent” designation refers to the focal length that would be needed on a full-frame or film 35 mm camera due to the smaller sensor on the D7100/D7200 (a 1.5 crop factor). So a 16 mm lens on the D7200 is equivalent to a 24 mm lens on a film camera.

Telephoto: With this new outfit, I jump from 300 mm to 750 mm equivalent with the 500 mm mirror lens. We’ll see how that works out. No autofocus and no vibration reduction. But, for covering the range between 300 and 600 mm, I do have the option of “digital zooming” (aka “cropping”) in post and I still end up with 6MP if I crop for the equivalent of 600 mm. I’m not certain I can actually print more than 6MP of detail with the mirror lens (or even with the 2x converter on the 70-200), so that’s up in the air. It is still an experiment, but not at great cost either financially or weight/size wise, and Robert is thrilled. Other than pinniped portraits on the beach and a few bird portraits, my longest lens images have not been as good as hoped. Many of my good critter images have come in under 300 mm.

The Samsung S10+ phone also allows me to easily copy SD cards. Mary Beth and I each carry a 256 GB thumb drive, the D7200 has a pair of 256 GB SD cards in it, and there is a 256 GB micro SD card in the phone. I’ve never shot more than about 3,000 images on a trip which converts to about 100 GB, so I should be covered for data backup on whatever trips we take in the future. The workflow will be to increment the folder number for each location/day of the trip. When we’re back in the hotel for the evening, the new folders will be copied to the phone and renamed with the final descriptive name (as we have been doing for all images). These renamed folders will be copied to the two USB thumb drives. This gives us five copies of the images in four locations (two in the camera, one each in my phone, in my wallet, in Mary Beth’s wallet).

Original article follows with all the gory details and thinking of my involvement with photography.

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New perspectives on squealing tapes

Martin Fisher from the Center for Popular Music at Middle Tennessee State University wrote me this morning and he identified a subtly different failure mode that I had not specifically thought of previously. I think the following best describes it and its remediation.

Manufactured with insufficient lubricant: This is a defect that appeared at birth, so while not a degradation (i.e. getting worse over time), it will still cause issues with reproduction. What distinguishes this failure mode from “Squealing, limited shedding” is that there is frequency modulation introduced during the original recording which was presumptively made when the tape was new. While adding additional lubrication will reduce the frequency modulation during playback (which is very important), it will do nothing to correct the recorded-in frequency modulation. The only method of correcting that is bias capture with the same head as the audio capture and running the resultant files through the Plangent Processes.

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DAT’s not good…but I’m back in the business

The long-term maintenance of digital formats that I do not get a great call for has become a burden. While I would like to have all formats available for all people, I have such a backlog of analog, that I will not be accepting digital-only projects in many formats that I used to.

The formats that I am currently committed to transferring are:

—DATs with two options:
         -straight transfer where we listen for glitches and look at the waveform for glitches (four Tascam DA-20 MKII)
         -error-logged transfer where the machine logs all of the errors it has concealed (Sony PCM 7030)
—PCM-F1 on VHS or Betamax (multiple machines and multiple ES-601 and PCM-F1 decoders)
—Sony DASH (3202 or 3402) 2-channel reel (two each Sony PCM-3202 and PCM-3402)
—MiniDisc (normal stereo in regular and HI-MD, but not porta-studio multitrack; multiple )
          (Sony MZ-RH1 Hi-MD Minidisc recorder with USB download; Sony MDS JE-530 and two other MD players)
—Digital Files on CD, DVD, hard drive, USB drives, etc.
—CD

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Acetate tape re-hydration

John Chester reminded me of an October 2005 post that I made to ARSCLIST that I had not mentioned in depth here. To keep as much information as possible in this one place, I thought I’d re-post it here with minor edits for clarity 13 years later:


Friedrich Engel, the retired BASF historian, gave me a present in a phone conversation (yes, to Germany, his English was far better than my German). You can re-hydrate acetate tapes.

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Images of Scotch (3M) tape boxes available

I was interested in the progression of the Scotch/3M tape boxes over the years, especially after Carmine Lauri contacted me because his father was in the picture of a chamber orchestra on the 1960s Scotch tape boxes. Click on each image to see a larger one. Any moire pattern you may see is the screening of the printing on the box beating with the pixel/dot pattern of your monitor.
   

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Studer A80 RC modifications for 1/2-inch two track and other modifications

In a discussion on 2012-01-20 in the New Studer list, Todor Dimitrov posted the differences between the record and repro boards between a 1/4-inch and a 1/2-inch two-track A80RC repro cards. Here are the changed components for the 1/2-inch version. There are five different oscillator versions in the manual, including one for 1/2-inch.

RECORD: C34=68pF
REPRO: R1=100K; R21=330

Note that the mechanical modifications between 1/4 and 1/2-inch tape handling may be substantially more complex in terms of tuning the transport. I know of no definitive notes on this subject. [Added 2013-10-09]

CBC A80RC Repro capacitor mod

I had previously posted in the original (and now reconstituted) Studer List on 2008-04-24 that there were other extant and possible modifications. Here is a slightly edited and reformatted version of that post:

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Sony APR speed experiments

We have been wondering just how far we can push the Sony APR-5000 capstan servo system, so we ran a few tests using an external oscillator feeding the reference port. Unlike Ampex, Otari, and Studer machines which use an external reference of 9,600 Hz; the Sony machines use an external reference of 19,200 Hz.

We found that the APR-5000s did not run reliably below 1.88 in/s — and that is achievable with a -50% varispeed already. It didn’t matter what the base speed was.

The APR-16 (cousin of the APR-24) did not run reliably below 3.75 in/s. But the good news was that we could bring 15 in/s down to 3.75 in/s using the external reference source. We were also able to run the APR-16 at 60 in/s, but takeup tension was a bit low.