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Year: 2006

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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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.

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.

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.

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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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.

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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Stripped hex head screws

The 2 mm hex head screws that hold panel modules and blanks on Studer A810s are easily stripped by slightly worn hex drivers. Studer used 2.5 mm hex head screws in the later A807, perhaps aware of this issue. Using PB drivers from the start will reduce the possiblity of this happening.

There are essentially two choices when this happens:

  • Slot the screw with a Dremel rotary tool and a small cutoff blade and use a slotted screwdriver to remove the screw.
  • Use some sort of Ez-Out screw extractor.

When I was confronted with this situation recently and I didn’t have an EZ-out of the correct size to bite into  the screw  without drilling,  I grabbed a T10 Torx driver and gently tapped it into the screw head. I pushed in hard while starting to turn and the screw came out.

Tools

High-quality hand tools are a must for working on high-end tape machines. I’ll discuss some of the specifics in other articles.

The tools that Studer supplied (when required) were made by PB Baumann, now PB Swiss Tools in Switzerland.

My preferred supplier (for North America) is Tool Lady. She also sells Wiha tools to complement the PB line. Barbara Christy, the original Tool Lady succumbed to cancer on April 11, 2015 after a four-year battle. Her daughter Rachel Straight has announced that she, in the guise of Tool Lady II, will continue the business.

Introduction

I have made a variety of static pages for my tape restoration Web site, but thought it was time to add a more user-friendly, article-based location to discuss various topics, tools, tricks, and techniques that I have come across in various ways.

What is easier to use than ready-made BLOG software, so I guess Richard is finally Blogging!

I hope you like this and find it of interest. Please let me know of any changes or topics you might like addressed.

Enjoy!

Note: This post has been put in every top-level category because it appears that a post is needed in each top-level category if the sub-categories are to be visible.

Note 2: The Tips  & Notes blog and the  Formats & Resources  static pages of this  sub-site replace the Tips and Resources static pages on the Web site. And, there is integrated searching across both the blog articles and the static pages.