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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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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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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

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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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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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.

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-16 Memory Locations (APR-24)

The 108 memory locations for storing setups is a real feature of the APR-5000 series tape machines. The APR-24 manual alluded to this but did not provide any instructions.

I have the only APR-16 that Sony ever made, but it is essentially the same as an APR-24. My APR-16 is running firmware version 5.01.06.0.

It appears that there are a total of 18 total preset locations in the APR-16 (and presumably the APR-24).

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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.

Is it really a Phillips screw or is it a Pozidriv screw?

Many pieces of equipment with cross-headed screws actually have Pozidriv screws rather than Phillips screws in them. This is especially true of Japanese equipment. [EDIT 2007-11-26] Or are these yet different JIS screws? See the updated post about this here.

I bought a set of Hozan [JIS] drivers, but now that I’ve learned that PB makes them [maybe] (see tools article) I’ll buy any additional ones from them. Pozidrive screws have “tick” marks between the slots–or should.

Here is an interesting explanation of the different screw heads in the context of cabinet/furniture making.

After some testing with both Phillips and Pozidrive drivers, it seems that some/many of the inexpensive screws that come packaged with home hardware-type items are non-descript and perhaps don’t meet either standard!

Digital Compact Cassette — DCC

I received a phone call today asking if I knew where to get DCC blank tapes. The person had purchased a used DCC machine on eBay or someplace like that because he “heard that they sound good.”

Audio mythology is growing. DCC is a perceptually coded format with bit reduction. Like MP3. Like the ATRAC system used on Minidisc. Not as advanced as MP3, probably (it’s older). Not as advanced as Windows Media (it’s older).

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Categories dcc

Transfer level settings

Audio levels (and their cousin loudness) has been an ongoing area of confusion and annoyances from the 1930s on. Adding digital to the mix has done little to simplify the situation.

Here we discuss some of the background and the relationship between the VU Meter, the Peak Programme Meter, and digital meters reference to 0 dBFS (Full Scale).

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Analog "Warming up" of sound & the use of obsolete formats in contemporary recordings

I received a phone call today from someone who wanted my opinion on a Tascam 238 8-track cassette recorder for recording his music.

This was like the person who wanted to know about the DCC recorder for the same purpose yesterday.

People keep hearing that “analog sounds great” or that this or that format “sounds great” and they want to buy in.

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Archival processing

As promised, I will respond to some questions that are asked via email by answering here in the Blog.

One of the things I’m most concerned with is the appropriate use of digital processing in transcription for cleanup or remastering of digital archival copies.   This includes both questions of when (if at all) processing beyond the actual A/D conversion is appropriate, and which are the techniques and currently available tools best suited to archival audio.

It’s a good question. To some extent, it depends on the client and the final use.

If the restoration/preservation reformatting is for an institutional client, then the first transfers should be as unprocessed as possible — at least the initial copies that are archived should be done that way. The main reason for this is that processing algorithms will always get better and they may hide some information that is useful to future researchers–information that today we consider “noise.”

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When is the 20 kHz limitation an issue? How big an issue?

The 20 kHz bandwidth of CD audio media may cause truncation of some material. Here is an example of a small amount of energy above 20 kHz in a symphonic recording. It is interesting to note that this is a 7.5 in/s recording done on 1970s prosumer equipment. I’ve said in my presentations for some years, most 7.5 in/s tapes are well-suited to 44.1ks/s 16 bit transfers, but there are exceptions. This shows one.

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Magnetic Developers — Seeing the tracks

This has been updated 2015-07 and now 2005-11. We ordered a new 1022 viewer from Arnold/Flexmag as the 2007 Sigma finally gave up the ghost and the 2011 Sigma that I had as a spare is not as good a performer for this application. As of the end of November, we are still awaiting a response from Sigma. Overall, I am quite pleased how well the “fresh” Arnold unit works and it appears more sensitive than the older 3M unit I had even when it was working well. This is now my top choice. It is not perfect, but fits the budget better and performs much better than the newer Sigma. It is also faster than the Sigma ever was.
Please look here, but there is still good information, below.
Two ways of seeing tracks on a tape are listed here. We’re collecting more in the comments.

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Sony APR-5000 Hum Shields not working

I got a call today from a friend who said the hum shields on a friend’s APR-5003 were not working.

I recalled this had happened to one of my machines in the past.

Removing the cover surrounding the heads will expose the mechanism—of course the heads and pinch roller need to come off first.

Cleaning and lubricating the rods and other parts of the linkage should make all well again.

I used Zoom Spout Turbine Oil.

How to archive recordings — a quick guide to resources on this site

You’ve been asked to digitize recordings in your collection and don’t have any idea where to start. There are  several resources on this site which might be of use.  

What I use is shown on my facility page. That\’s one of the main reasons it is there. If I’m using it, it’s because I like it or it solves a problem for me. If I’m not using it, either I don’t have an opinion about it, won’t spring for it, or don’t like it.

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VCR Tracking and Cleaning—A guest article by Jim Wheeler

There was an off-line discussion about VHS-Hi-Fi tracking and breakup in Hi-Fi playback and how to correct it. I brought Jim Wheeler into it, and he agreed to write this article. —Richard

I invented the automatic tracking system in 1976 but it is pricey. If you want to pay about $2,000 for a pro-VHS machine, you can get true auto-tracking. Manual tracking works for most tapes. If not, there was a problem with the recording VCR. Alcohol is not good for cleaning heads and tape guides. I always use Xylene and you can buy Xylene at hardware and paint stores. Do not use Xylene on a pinch roller! Have your window open when you use it. I sniffed Xylene for over 30 years and am still okay–okay–okay….I recommend using Xylene for cleaning all components in the tape path except the pinch roller. I recommend Isopropyl alcohol for cleaning pinch rollers. [Some of us are using Formula 409 on pinch rollers—it depends on the pinch roller and its application—Richard]

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