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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.

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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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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Tape Degradation—Introduction

This is a general article to provide some information on the subject. More should follow.

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

There are multiple modes of degradation and it depends on the type of tape.

Acetate Tape

  • Degrades through drying out (hydration has helped in some cases)
  • Breakdown of the base through “vinegar syndrome” and possibly leading to total decompostion (although that has not been seen for tapes on any large scale)
  • Damage from heat
  • Damage from mold/fungus
  • Loss of Lubricant is probably rare in acetate tapes. Few examples of it have been found.
  • Freezing acetate tape (especially) is considered bad as many of the formulations included fatty-acid lubricants. Remember, this was from the 1940s and 1950s and one of the best lubricants of the era was sperm oil.

Polyester tape

  • Binder hydrolysis (or sticky shed syndrome [SSS]) is the largest challenge faced with tapes from the 1970s-1990s. This can be partially reversed through incubation or heat treatment. While this link may not be complete, it is a great introduction.
  • Loss of Lubricant (LoL) can be severe and can possibly be combined with binder hydroysis.
  • Freezing is also not recommended for polyester tapes due to the potential of that tape also containing fatty-acid lubricants.

Obviously all tapes can suffer from mechanical damage and poor winds.

I expect to be discussing aspects of this in greater depth, but it is a complex subject and contradictory reports have been generated.

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.

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

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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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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Powering Wall-Warts

The regulatory climate and economics will support a wide variety of “wall-wart” power supplies for the foreseeable future. These are, at best, a headache to deal with. Some of the ways I’ve dealt with them are:

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Computer audio interfacing

It just came to my attention that computer architecture is transitioning from the PCI interface to the PCI Express interface.

This supports my contention that Firewire (IEEE 1394) and USB 2.0 are the preferred methods for connecting high-quality, high-resolution audio interfaces to computers.

While I have two RME Multifaces (the original, not the Multiface IIs shown in the link) that use dedicated PCI cards, this means that if I purchase a new computer with a PCI Express interface, I’ll have to purchase two new PCI Express interface cards for the RME Multifaces — and hope that RME makes it at the time I need it. Many users have expressed satisfaction with their Digital Audio Labs CardDeluxe.

This sounds a lot like the Zefiro Acoustics ZA-2  ISA card that is languishing in a Dell Dimension XPS PII 333 MHz machine.

My recent foray into an audio interface via IEEE 1394 was the MOTU 828 MK II. So far, I am happy and it’s finding uses in the studio as well as the remote notebook-centric applications I originally acquired it for.

I would think that a good audio interface might last longer than a good PC, so consider this approach.

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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Do’s and Don’t’s of tape handling

MINIMUM Tape Handling Requirements Checklist

This checklist is not a complete guideline. It contains only those items that experience and testing show will have an immediate or severe effect on magnetic tape. Failure to adhere to the items on this list may cause premature loss or deterioration of magnetic tapes and should be considered misuse of the medium. These are minimum handling requirements that summarize good practices.

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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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Demagnetizing recorders and heads

Demagnetizing tape heads and recorder parts is a ritual of magnetic recording. If any part that touches the tape is magnetized beyond a certain level it will begin degrading the tapes played on it.

While early machines may have had an issue with magnetization, most late-model machines rarely become magnetized. The source for real information on this is Jay McKnight’s Magnetic Reference Lab Web site.

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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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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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Project Notes: Crosstalk on a cassette

I received a cassette from a client and he complained that the previous recording was audible as well as the new recording.

There are several ways this can happen:

  • The erase head can be dirty—this usually leads to high frequencies being erased and lower frequencies still audible
  • The erase head can be misaligned—this often provides a partial erasure, but careful use of track selection can find a section of track with less crosstalk.
  • A similar problem occurred on quarter-track reels with misaligned record heads where recordings from the opposite direction would invade the tracks for the forward directions. Again, a specially adjustable narrow head usually solves this.
  • A completely non-functioning erase system—this is what we suspect happened with the current project. There were no track dissimilarities nor any other way we could find, including looking at the tape with the 8-track cassette recorder to separate the underlying, unwanted recording from the wanted one.
  • A totally unrelated mechanism that may sound the same is if the microphone or tape recorder picks up a broadcast or other radiated signal and records that along with the desired signal.

We opted not to proceed with any noise gating as it would not improve the overall audio quality for listening and may actually impede transcrption.

While not a success, we were able to confirm to the client that there was no way that could preserve the fidelity of the desired sound and remove the undesired sound. The desired interview was completely intelligible and could be transcribed. It was just distracting to listen to.

Noise Reduction Basics

\”Noise Reduction\” is a potentially confusing topic, partially because it has come to be used to mean two different things.

  1. Today, it means removing noise from a recording by means of a single-ended post-production device or plug-in, such as Noise Free Pro by Algorithmix that I use (among other tools).
  2. Historically, the term was used for a double-ended process where the dynamic range of the program material was reduced in an unobtrusive way, transported by the noisy channel (be it tape or broadcast) and then expanded in a complementary fashion at the end/output of the noisy channel. These devices were generally referred to as companders (a contraction of compressor/expander).

When reviewing old tapes, they may be marked in various ways to indicate their noise reduction compression, or processing. As of this writing, there are no software plug-ins that accurately mimic the action of the hardware compander acting as an expander. We use actual companders from the original systems when restoring tapes made with these systems.

We currently handle nine different formats from four manufacturers and are always on the lookout for more. Most manufacturers sold a variety of systems tailored to the needs of different kinds of transmission/recording channels

See our special page under formats (click here) to see some of the information we’ve gathered about noise reduction techniques used over the years. Check back as we uncover additional formats and information.

Alternate tape equalizations—Teac Extra Efficiency

While the Ampex Mastering Equalization is well documented on this site and at the MRL site, and standard equalizations are detailed at the MRL site on page 3 of this document, I am always amazed when I discover additional, supported tape equalizations. Certainly there have been proposals for alternate equalizations. Jay McKnight has published a paper (here) about this. This post is about something different.

Teac Corporation, with their X-2000M reel-to-reel tape recorder included a button called “Extra Efficiency” to be used with then-new tapes that had double the coercivity of standard reel-to-reel audio tapes. This changed the recording equalization (and the bias and possibly the reference levels) to better make use of the new tapes to improve the overall sound.

What was fascinating here is not that they used the IEC standard equalization of 35 μs at 15 in/s, which was standard in Europe, but that they also invented their own standard and used 35 μs at 7.5 in/s as well! Not content with that, they invented yet another standard of 50 μs for 3.75 in/s.

The NagraMaster and StellaMaster equalizations are also non-standard and were probably the most widely adopted equalizations after AME, but who knows how widely used this Teac EE equalization was and who knows what tapes are in archives that had this equalization incorrectly applied.

I have been informed that it was only intended for the consumer market.

DSS and other compressed digital files in an oral history archive

With budget limitations, it appears that oral histories are being recorded with little thought to their long-term preservation. While this appears to have been the case in the past as well, with purchasing agents buying the cheapest white-box tape that they could find, continuing this into the digital age needs to be reconsidered.

The cost savings in using bargain-basement digital speech recorders are offset by the labour required to reformat these files upon their receipt by an archive and also the fidelity of the recording suffers, and with fidelity, intelligibility also suffers.

DSS was an industry standard agreed upon by Olympus, Grundig, and Philips in 1994.

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The beginning of 3M 175 squeal ?

UPDATE: March 2008…Cold playback (see this article) seems to work with the two tapes mentioned in this article, 3M 175 and Sony PR-150. We’ve had confirmation from several sources who have tried it.

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

Fellow restorer Doug Pomeroy sent me a photocopy of Herman Burstein’s “Tape Guide” article from the May 1977 issue of “Audio” magazine. Robert Coe of Manchester, CT, wrote in saying “…some of these [Scotch 175] tapes have developed a high frequency chatter or squeal which is mechanical and can be stopped by rubbing the tape with a light coating of talcum powder. The squeal only occurs on the Scotch 175 tape even when used with several different brands of tape machine.” Burstein replied, “Yes, I’ve heard other complaints about squeal, sometimes involving Scotch tape which is not surprising in view of 3M’s large share of the market, but yours is the first complaint about 175 tape.” He went on to say that another 3M tape exhibited this but it was limited to the batch and 3M replaced it.

We do not recommend the talcum powder approach as it overall has proven to be a bad idea since it gums up the machines and increases spacing loss more than other solutions.

Doug is currently having a joyous bout with 175 but Art Shifrin apparently has a proprietary mechanical fix to the tape deck that allows playing 3M 175.

We are researching more about 175 and hope to have updates. The use of decamethylcyclopentasiloxane (D5 or cyclomethicone) has had mixed results with 175 and Sony PR-150, another known squealer.

Second seminar complete and was a success

We have recently completed our second audio tape restoration seminar.

We had three great attendees. One of them, Andy Kolovos of the Vermont Folklife Center shared these comments:

I want to thank you again for the workshop. I’m certainly still assimilating stuff in my head, but it was terrific. I learned so much… Through these workshops you’re doing the archival field a huge service. The ability to tap into your experience and take what we learn back into the world with us enriches everyone. Because you are willing to share your knowledge, skill, and passion with those of us who love these audio resources, work with them on a daily basis and are eager to learn all we can about their care, more of the aural heritage of the world will survive into the future. Your generosity is wonderful! Thanks again!

You can see the brochure for our November 2005 seminar here.

Comments from the November 2005 seminar are in the brochure  for the May 2006 seminar.

The first three of the four days we were together about 13 hours a day (including dinner at various restaurants) and we didn’t stop talking audio. We covered a LOT of ground and the questions and discussions were great.

Cassette Equalization: The 4 dB ambiguity at 16 kHz

There have been rumours that Nakamichi used a different cassette standard than the other manufacturers. This is not really the case. Everyone thought they were using the same 3180/120 or 3180/70 microsecond equalization as specified in IEC Pub 60094-1, 1981. There is further discussion from 2010 here.

As I understand the history, both Nakamichi and STL in the late 1970s discovered that when they made calibration tapes based on the published time constants in the standards, their response showed that the then-common BASF alignment tapes were approximately 4 dB high (hot) at 16 kHz.

It is assumed that BASF, who made the calibration test tapes made an error in calibrating their reproduce heads’ response in one of two areas:

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Hard disk formats for interchange

The question of how to format hard disks (i.e. what file system to use on them) for easy interchange is another FAQ. A recent experience brought home the fact that it is more complex than one might hope. The computer industry is headed towards universal readability, but it is not there yet. The most-able-to-be-read-and-written format appears to be FAT32, although my friend Eric Jacobs makes the point that NTFS is a more robust hard disk file system, and I have to agree.

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StoryCorps experience including equipment discussion

My friend Susan Kitchens and her brother took their parents to the StoryCorps recording session in Los Angeles a few weeks ago. She blogged it here. One of the neat things is that between her article and the discussion she and I had in the comments, we have a good handle on most of the equipment that was used in the trailer. It’s a good selection in my opinion and shows how simply good-quality recording systems can be set up. Further discussions from a StoryCorps representative have shown how clever the setup is.