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Microphone Powering Schema

In addition to my business of transferring tapes, I also record a few community groups for fun. Someone recently gave me an older Sennheiser MKH-804 interference tube (“shotgun”) microphone. Finding information on how to connect it proved more difficult than expected.

In the 1960s, transistorized microphones from AKG, Neumann, Schoeps, and Sennheiser became available. There are several niches of early microphone powering that continued on for many years. Perhaps the easiest way to look at it is backwards.

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An unorthodox dual-WAN approach

Since moving to Aurora in the fall of 2004, and going into audio tape restoration full-time, I have struggled with the correct mix of connectivity. My rather unique needs require that I have upload speeds as fast as reasonably possible.

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Kodak Durol triacetate tape with bad vinegar syndrome

I recently received two 7-inch reels of Kodak Type 31A Triacetate tape (1250 feet, Durol Base) that smelled of vinegar even before I got the envelope open.

These tapes were badly warped due, most likely, to the vinegar-syndrome induced differential shrinkage. Other factors may have been poor winding during long-term storage (I had received them after several attempts to play them on another machine).

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Zoom H2 line input

The Zoom H2 HandyCorder is perhaps the lowest-cost digital recorder on the market that provides reasonable and useful results. While I have a Sound Devices 722 for my more serious work, I bought the Zoom to test it out to see if it could be part of a simple tape digitization system for archives on a budget who wish to do the work themselves. It does this reasonably well.

As with much equipment–and especially with lower-cost equipment–the performance specifications and the actual operational data is not published. There are reports of the H2 clipping on the line inputs in some of the reviews and it appears that a lack of understanding how the inputs were configured exacerbated that situation.

There is nothing wrong with the line inputs on the H2. BUT there are some caveats:

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Rechargeable battery solutions 9V, AA, AAA

Battery technology continues to improve. In 2007, I bought some Sony fast-charge nickel-metal-hydride (NiMH) AA cells and charger. They have worked well for digital cameras, electronic flashes, and a portable audio recorder. NiMH cells are available in major stores and some offer long-shelf-life-per-charge and come pre-charged.

Recently, I did a thorough search for 9 V rechargeable batteries for wireless microphones at church. I was pleased to discover that iPowerUS (they have a Toronto office) was able to provide lithium polymer 9 V batteries that far outperformed the available NiMH offerings. We bought one DC9V charger and eight DC9V-520mAh batteries for alternate use in four wireless transmitters that we use regularly. We expect this system to pay off in a year or less.

I also bought their GC-60 tester/charger for my NiMH AA and AAA cells which, so far, looks excellent. Both chargers come with a “wall wart” and a car cord.

See updates in this article.

Sony APR-5000 head assembly problem

I was having slightly intermittent connections on one head assembly on a Sony APR-5000 and was concerned as to the cause because the 78-pin head connectors are essentially unobtanium and a headache to change.

As I installed and de-installed the head, I got to thinking that the connector might not be positioned correctly (i.e. perhaps the wrong hardware had somehow found its way into the connector mounting system.

When I measured the bottom (oriented as if the head were mounted in the machine) face of the connector mounting flange referenced to the bottom of the mounting posts (using a straight-edge across two of them), I discovered that, indeed, this connector was recessed about 25 mils (0.025″) further into the head assembly than several other ones. Adding a 25-mil thick washer should solve the problem.

This is posted in case you’re scratching your head with a similar problem. This is something I wouldn’t have immediately thought of. I don’t know if this was caused by aftermarket work or if it perhaps represents a manufacturing error.

40th Anniversary of Apollo 11 Moonwalk and the loss of data

There has been much discussion over the last few years about finding and saving original tapes of the Apollo 11 Moonwalk videos downlinked from the moon. There is also an exciting project going on to restore and digitize the Lunar Orbiter tapes from more than 40 years ago.

The Lunar Orbiter tape digitization folks have just posted a commentary that bears reading by all archivists who are holding tapes. You may link to it here. The main site is www.moonviews.com

NASA, in their press conference yesterday held at The Newseum, admitted that the original 14-track 1-inch instrumentation (IRIG) tapes that contained the slow-scan video direct from the moon were most likely recycled and reused for later missions. Apparently, over 350,000 reels of instrumentation tape were recycled by NASA over time. No one apparently thought to preserve the 45-odd reels of the original moon walk.

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Dangers of old tape recorders for playback; using the elevator head

We are currently working on some un-published tapes for a major Canadian folk artist. We have a 7.5 in/s 2-track stereo recording that was one of (if not the) first studio recording of this artist from circa 1972.

At some point, this tape was played on a 1/4-track machine that injected hum onto the left channel. Here’s what the magnetic viewer showed:

hum_overwrite_dsc_0571

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Long-term stability of different batches of Ampex 456 – a guest article by Gary Galo

Here’s some info that might be useful concerning which batches of Ampex 456 are good and which have sticky shed problems.

I recently unearthed 26 brand new 10 1/2-inch reels of 456 from 8 different batches. I checked one reel from each batch by playing them back and forth at 15ips (I only played the bad reels in one direction – that was enough!). The following batches were bad:

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Compander-type Noise Reduction Systems

Note: This information has been incorporated into this page which contains a more in-depth discussion.

I received an urgent phone call yesterday from a man who had digitized several reels of 2″ 24-track analog recordings that he wished to re-mix.

The tapes were originally recorded in about 1978-1979 and he said that he needed them to have Dolby C noise-reduction processing applied to the files.

I did a bit of research, as that did not sound correct from an historic point of view.

Here is an approximate chronology of the major noise-reduction systems and their dates of introduction:

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End of the 3.5″ floppy disk

CNET reported yesterday that Sony will be stopping sales of its 3.5-inch floppy disk media in March 2011 in Japan. Apple stopped supplying these as standard equipment in 1998 and Dell ceased that practice in 2003.

While this medium is not widely used for audio or video, there is, I suspect, still a large amount of ancillary data kept in this format. I will look through my collection and see if there is anything else I need to capture to my servers before my drives die.  I would not entrust anything important to this format.

We stopped using these about three or four years ago, with the last holdout being school work brought home. Now, even that is done on USB keys.

Cassette equalization redo

There has been much discussion on some web fora about the differences between different brands’ cassette equalization standards.

As I stated here in 2006, there is a 4 dB ambiguity at 16 kHz.

Many things conspire to make this 4 dB ambiguity essentially meaningless in a generally low-fi medium. The only reason I’m mentioning this now is that I’ve been bombarded with email from more than one participant in this discussion and apparently there may be some editorial judgment attached to what is posted.

Jay McKnight has graciously permitted my posting of his comments to me:

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IASA TC04 Guidelines on the Production and Preservation of Digital Audio Objects available online.

The International Association of Sound and Audiovisual Archives (IASA) has released their landmark Guidelines on the Production and Preservation of Digital Audio Objects as a free web (HTML) edition, available here.

I provided some information for the listing of tape equalizations, and I find the compiled table (here) most useful.

Thanks to Kevin Bradley and the IASA team for their work in making this available. If you want a PDF copy, join IASA and it’s available.

Another NAS contender…

revised 9:15 AM to add Synology

I was reading some additional NAS discussion on a photography list serve and was introduced to yet another NAS vendor that deserves consideration, QNAP. They appear to have wide distribution in North America (I found two online retailers that list them, CDW.CA and CanadaComputers.com. While the comparison was made to the Drobo products in the discussion I saw, these products appear to be similar in pricing and quality to Thecus and Netgear and offer some interesting options. Thecus units are more difficult to obtain, but Netgear units are also available at the two online dealers listed for QNAP. Yet another name just came up in the discussion, Synology. QNAP, Synology, and Thecus are all headquartered in Taiwan, while Netgear is headquartered in the U.S.

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Open Source software…and other tools

I have been having a lot of fun recently looking for specific software tools that avoid having to purchase multiple licenses of the high-priced programs. Here are a list of my picks of free and low-cost software tools. I am sticking with Samplitude Professional for audio and Adobe Photoshop and Adobe Photoshop Lightroom for photo-graphics. The other alternatives, however, are wide open.

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Track Configuration page updated

I added a Track Configuration page to the resources hierarchy in the sidebar at the right. This points to other resources on the web to provide further insight into the various analog audio track configurations. There is also a brief note there about the variation in the two-track, half-inch format. These differences are minor, but they could be a source of some problems under some extraordinary circumstances.

This page was updated 2012-01-05 to provide track widths on higher-density audio multi-track formats.

A link to the Studer track dimensions page was added 2012-01-06.

Updates posted for “winding tapes for long-term storage”

There was yet another discussion about winding tapes for long term storage. This time it was on the Society of American Archivists list. While it was focused on VHS tapes, where it was decided that it was more important not to leave the tape in the middle with active content exposed, some discussions of the mechanics arose and I have added them as comments to the original post, which is available here.

Open Source software…and other tools II

This is the second installment of my open-ended quest for great software. The previous (and inaugural) article is here.

The excitement is that the current version of LibreOffice has removed a good deal of the startup sluggishness. While still not as fast as MS Office 2003, remember with LibreOffice, you are starting the whole suite essentially. There is an option to load it at startup, which I do not use.

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Update (2012-08) Kyread spray-on magnetic viewer fluid

In several articles on magnetic viewers, we have discussed the spray-on Kyread product.

GOOD NEWS! The company is back! I received a phone call from Ryan Blackwell this afternoon and he pointed me to their new website. The company name is now Kyros Technologies LLC.

Note their jump into the 21st century with a real website and great domain name: magneticdeveloper.com — they even have a shopping cart for online ordering. This is apparently the same product I’ve been using for the last eight years.

Watch those insects!

OK, this is not directly related to audio, but three audio people I know have been bitten by insects this spring and have suffered greatly for it. One was bitten by a spider in California, one almost died from a flea bite in Texas, and another received a suspected spider bite in Pennsylvania…so be careful…you never know where nasty insects might be hiding…maybe even under a tape box!

If you are worried about what to do, a friend, though a staunch vegan, squashes spiders. Of course, certain spiders are good and eat other insects, so this is just another one of those tough decisions in life.

And then there is mold. A good friend’s life was cut short by interaction with mold, though he was a smoker much of his life, so I’m certain that contributed to it.

As my Dad used to say, “you don’t get out of this life alive”, but he made a good run for it, living until age 93!

Slide Storage Warning – Airequipt 2 x 2 Slide File

Over the years, I’ve used various methods of storing 35 mm colour transparencies. Until 1992, I used mostly metal slide boxes, but I do have about five Airequipt 2 x 2 Slide Files which are a hard plastic. One of them was sitting on a painted steel shelf and I found some oozing degradation components that were oily/greasy and rust where the paint on the shelf was scratched (probably prior to the box being placed on it).

These boxes have bubbled to the top of the priority list. The interior and slides seem to be fine…for now, and the other boxes are showing little or none of the symptoms of the one (which is probably not the oldest). The slides in this box date from 1983, but the box is almost certainly older. The Logan and Brumberger steel files are, as expected, holding up well, but I am migrating the images to hanging slide sheets from Transparent Office Products. I suspect that I’ll end up with about 2,500 sheets with probably 16 slides/sheet on average…and that will fit in seven file cabinet drawers (2′ deep). These sheets were originally sold by Franklin Distributors until Transparent took them over about half a decade ago. I bought my first sheets from them in 1991 or 1992 and they are still doing fine. Some other alleged to be archival sheets from the same time did not do as well.

We are scanning all of the images as we move them using a Nikon Coolscan 5000ED with SF-210 slide feeder.

Playing full-track mono tapes

About ten years ago, when I transferred the oldest tapes in the United States as part of the Mullin-Palmer collection, my good friend Don Ososke pressured me to use a full-track head for the project. I had started transferring these full-track tapes with a Woelke NAB stereo (two 80 mil (2 mm) tracks) head and recording both channels. When I obtained a Nortronics full-track head, the difference was night-and-day. The full-track reproduction sounded fuller, smoother, and quieter. There were no tracking problems to speak of that would cause azimuth wander large enough to create a “flanging” or “phasing” effect of in-and-out high-frequency loss.

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Agfa PEM-469 success

We had success transferring two reels of one-inch Agfa PEM-469 tape that was shedding and leaving a waxy clear-to-yellow exudate on everything. We were happy to get through these and recover the content. This is discussed in more detail towards the bottom of our Degrading Tapes page—hopefully the most up-to-date resource on the Web about problem tapes. Please let me know if you would like to help me add anything to the page. It is there for everyone struggling with old degrading tapes. If you haven’t looked already, please look at my paper on the subject.

Gap Length

This page provides a table of signal wavelengths for different speeds and frequencies. It is sometimes useful in understanding bandwidth limitations at the high end for a particular head. The first null occurs when the wavelength of the signal is about 112% of the optically measured length of the gap. A common place to set the gap length is for a 4 dB loss at the highest frequency of interest. This corresponds to the half wavelength indicated in the table below. See Mallinson, John C., The Foundations of Magnetic Recording, Academic Press, San Diego, 1993. pp 95–96.

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Speed variation with unmatched reels

I received an interesting question from a European tape user with whom I frequently correspond:

“Is there any speed variation when playing a tape with different hubs on the supply reel and take-up reel?”

And I replied:

You raise an interesting question. The easiest answer to this is simple:
There is a risk of speed variations throughout the reel if the tape tension varies throughout the reel.
followed by the corollary:
This effect is made worse if the condition of the capstan / pinch-roller system is degraded.
and
Some capstan / pinch-roller / constant-torque systems handle this better than others.

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Playing a squealing reel of Sony PR-150 tape using D5 (Decamethylcyclopentasiloxane)

Today I worked on a batch of five Sony PR-150 7-inch reels recorded at 3.75 in/s in one direction, two-track mono. One of the five reels showed marked shedding during fast-wind/rewind (to get the original reel as takeup and to check the tape pack). Four of the five reels played fine. This one squealed horribly. I ran the tape up and back over the dispenser and then fixed it in position for running the tape over it during the playback session. Once again, D5, Decamethylcyclopentasiloxane, CAS Number 541-02-6 comes to the rescue. The lovely thing about D5 is that it evaporates.

APR-5003 with D5 dispenser

Is this better than cold playback? I don’t honestly know. Both work. This is easier if there is no reel machine standing by for cold playback (which there was not today). I keep a Nakamichi MR-1 in the refrigerator so it is ready to go when I need it. The Studer A810 I put in the fridge did not like it. The capstan motor seized up AND the heat output overwhelmed the refrigerator’s capacity to cool. I suspect the APR would also overwhelm the refrigerator’s capacity. Also, it is much easier to lubricate a reel than a cassette.