The critical factors are:

• Azimuth
• Direction
• Polarity

The azimuth of both sides needs to be the same. If the two sides were recorded at different sessions and/or on different machines, then there is no guarantee that azimuth will be the same on both sides. In a large-volume project, this can be addressed by installing two repro heads, one for each direction, and adjusting azimuth separately. This does not work well for stereo tapes with different azimuths because any temporal perturbations in either the recording or reproduce passes will result in severe stereo image shift. If a record head had azimuth scatter between the two channels, it is best to split the difference, if possible without severe high-frequency attenuation.

Obviously, the direction of the playback needs to be reversed in the DAW (Digital Audio Workstation) software, but that happens pretty quickly on a current computer.

Not-so-obviously, the polarity of the signal is also reversed when played backwards. That, too, can be addressed, possibly in the same pass or, worst case, a separate pass in the DAW software.

This is not recommended for any tapes using noise reduction such as Dolby or dbx, nor for the highest quality of music. However, most two-track tapes recorded on both sides are not of this quality.

Related posts

About 2004-2005, I had some full-track 7.5 in/s tapes to transfer that had been badly warped and found that there was enough azimuth wander that the tapes sounded better using one channel of an NAB stereo head. If I used the full track head, while the results were quieter, the azimuth phasing was unacceptable. At that point, I was using a Studer A810 for this type of transfer.

A few years after that, I was asked to recover audio from a 7.5 in/s full-track tape that was part of the Monterrey Jazz Festival. The client was very impressed at my efforts. I was able to use the full-track head, but one of the major differences was that this time it was on a Studer A80RC rather than a Studer A810 and the difference in tape guiding seems to have been the “magic” in that transfer.

The rule is use the most stable transport available and the widest head available to capture as much of the sound as possible without annoying azimuth-wander-based high-frequency combing/phasing effects.

If you use a head narrower than the full-track width, there may be objectionable low-frequency fringing that would need to be compensated.

Related posts

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.

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!

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.

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.

The loss of the original IRIG tapes of the moonwalk is truly sad because this data could be re-converted to standard television formats using far superior methods than were available in 1969. There may be 2-inch helical Ampex VR-660 video tapes still extant of the slow-scan data,  but those have not surfaced. It appears that all surviving copies of the moonwalk videos are ones that had gone through optical standards converters. An optical standards converter is one that has a monitor displaying the image in real time in the transmitted standard and a television camera taking a picture of that monitor using the desired standard. Even the Australian Broadcasting Corp. tapes would have gone through this type of device, although they would be in PAL rather than the U.S.’s NTSC versions.

Lowry Digital is doing a great job of restoring what they have, but the Polaroid screen shot that survives of the slow-scan monitor is alluring of what could have been preserved. More information is available on the Parkes website and from NASA.

Vigilant migration of data as new storage techniques become available is the only way to assure long-term preservation. Even if the IRIG tapes are found, we are almost at the point where the tapes would be un-decipherable. I think one of my machines could play them (I say think as I’ve never tested it to full 500 kHz bandwidth), but I don’t have the specialized video decoder. NASA apparently preserved some equipment should the tapes ever show up.

This also raises another spectre. We MUST be selective as to what we keep in our archives because if we keep everything we won’t be able to afford it–or find it. This is one of the key jobs that archivists do. However, blindly following retention practices, as was done by NASA for the IRIG Apollo 11 tapes, needs to be tempered by historians as well. Certain small subsets of data (moonwalk slow scan video) are much more important than others (astronauts’ blood pressure and other biometrics throughout the entire flight).

All organizations who keep archives need to address this. In a generation (or less) if we save everything, it will become an overwhelming burden and the high points will be lost if they are not properly indexed.

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:

1. DO NOT use the input level control on the line inputs to go below 100 or the preamps will clip before the signal reaches 0 dBFS.
   ALTERNATE WORDING (thanks Greg H.):
   Set Zoom H2 RECORD LEVEL to 100 or greater to avoid clipping at the Line In preamp stage.
2. Use an external attenuator with the gain set at 100 to avoid overdriving the line inputs.
3. The noise floor is not spectacular, but is not too bad. With the inputs terminated in 150 ohms, the peak noise was -70 dBFS, but that improved to about -85 dBFS or better, measuring it as an A-weighted rms figure, which is how most noise is measured. While this certainly isn’t what one would expect out of the Sound Devices, it is far better than the 50-60 dB(A) that one can achieve with an analog cassette tape without Dolby.
4. The maximum input level to the line input should be no more than -5 dBV or -3 dBu.
5. Try to avoid clipping as there appears to be a delayed recovery in some instances.

With this information, you can optimize a pad between the source and the H2 line input so that the recorder is never overloaded. Try to keep the levels as high as practical as there is a relatively limited dynamic range. On the other hand, I have found that the recorder noise is not objectionable even when I’ve boosted the levels 20 dB for a quiet choir piece from our church. The room ambience totally swamps the recorder noise–at least as far as I hear.

The H2′s internal mics are reasonably good for many purposes. While I still prefer the SD722 for many things, I think the H2 is one of the better oral history conversation capturing devices I’ve seen. It uses SDHC cards which may require a new card reader. Don’t use the built-in USB connection unless you’re recording MP3 files as you’ll be there all day. The internal card-reader mode is limited by the USB 1.1 interconnection. This interconnection is adequate, however, for using the H2 as a 16-bit live audio interface/microphone connected to your computer (at either 44.1 or 48 ks/s). The unit will record up to 96,000 samples per second, 24 bits,   but many of those bits will be noise.

Please let me know if this has helped or if you have any questions or comments.This work was done with version 1.50 of the H2 firmware.

The British Libary has now published his Handbook (click here).

Teaching people how to identify tapes that are suffering from sticky shed syndrome is often difficult.

I would like to propose that a careful inspection of how the tape comes off the pack may be a good way. Please provide comments as to how it’s working for you.

The tape should come off the tape pack at a precise tangent to the tape. If the tape starts to adhere and not pull off straight, that is a sure sign that the tape needs baking.

Of course, don’t bake acetate tapes even if they show this indicator, but on the last batch of questionable SSS tapes, I’ve been looking at this and it’s a fair indicator, and it seems to show at the outer edge of the pack.

More than one “test” or “factor” is needed to be sure, but this one is looking good.

Another almost sure sign of SSS is brown oxide and black back-coat.

While this is a theoretical problem, few if any good mono recorders are available for reproducing these tapes anyway, so most of us in the domain transfer field use good quality stereo machines for all cassette transfer work.

This is an interesting anomaly that should not effect operations. If you had a full-width mono head, there would be at most about a 4 dB improvement in signal-to-noise ratio vs. using one track of a stereo head (which usually results in better sound). Since the premium cassette decks, such as the Nakamichi Dragons that I use, provide very low wow and flutter, flat frequency response, a means to adjust azimuth of the play head, and gentle tape handling, all of these benefits outweigh the 4 dB or less reduction in signal-to-noise performance. If the tape hiss is a real problem (as opposed to noise recorded in from the recorder’s electronics), some of it can be effectively removed using a noise-reduction plug-in. Generally a 4 dB noise reduction in a good plug-in is transparent.

We do recommend archiving both tracks in a professional archival scenario.

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).

Common practice in audio archiving is to use 128-bit checksums, although 160-bit checksums are available. The other common practice is to take the entire filename, including extension, and add a second “MD5″ extension to that. The *.*.md5 file contains the MD5 checksum plus generally the filename.

An alternate configuration is to create one file named checksums.md5 for the entire folder to save downloading effort.

While there are many options for creating MD5 checksums, for Windows, FastSum is a convenient and low-cost package.

At any point in the future, to verify your files, you create a new MD5 checksum and compare it to the ones that were created when the file was created. If they match, you know your file has not changed. The likelihood of both the original file and the checksum file changing so that they still appear valid is essentially nil.

Some applications, like D-Space, check the integrity of all the files in the system on a regular basis using MD5 checksums.

If you receive WAV files from me, more than likely, you will also receive MD5 checksums in the same package, be that on a DVD, hard drive, or via the Internet.

It only takes a minute to create these and it truly does offer peace of mind.

I have just completed about 25 seven-inch reels of circa 1960-1965 acetate tapes (Scotch 111A, Audiotape, Soundcraft, Ampex 511, etc.) and about 20% of the tapes showed evidence of spoking after being played on the A80. These were rewound (approx 120 in/s under capstan control) on the Racal Store 4DS and then played at 15 in/s back onto their original spool.

With the heads removed, there are no fixed guides that contact the tape, just the two rolling tension guides and the capstan.

For photos of the Racal Store 4DS, please look here where I discuss its use (with head/guide assembly) for playing squealing tapes.

Please also read this post for a “do not try this at home” note.

I had the pleasure of speaking with Nadja at length about her work and I was very impressed by her approach and knowledge — as well as her practicality in getting the job done.

This document is a must-read for anyone planning a digitization project. While it is not as detailed or comprehensive as the Sound Directions publication, it cuts to the heart of what we’re trying to do in digitization. Starting with as good a playback as possible is the key to obtaining a good digital representation of the original. It also provides excellent photographs of various failure modes — and some are truly spectacular.

I must provide a disclaimer here that this website graciously links back here as well.

Oh, and the discussion started about images, but it pertains equally to audio and video. Ike was certainly clear on his thoughts about data tape. As I see it (without following it too closely), the marketplace is consolidating around LTO and appears to be shrinking, so maybe he’s right. I’ve stayed away from data tape in favour of an all-disk solution (for approximately 3 TB of storage at the moment).

When looking at storage for audio, consider a track-hour (i.e. a mono program) at 96,000 samples per second, 24 bits, is about 1 GB, uncompressed. 1 TB is about 1,000 track-hours of material at the normal high-resolution sample rate and bit depth…and that currently fits on one physical drive.

We continue to receive poorly wound tapes and are able to play them successfully. So why the quandary now? The reason is that I read portions of another Bharat Bhushan book, Mechanics and Reliability of Flexible Magnetic Media, 2nd Edition, New York, Springer, 2000. Referring to several research papers he makes a compelling case that tapes should be rewound annually if subject to storage environment fluctuations and every 3.5 years if kept in a climate controlled storage area.

If we think about the two types of stresses on each layer in the pack, this becomes more clear. There are “hoop stress” which is the circumferential stress in that individual layer and the “radial stress” which is the stress in the direction of the centre hub.

Low interlayer pressures, which predispose the tape stack to ILS [Interlayer Slip], are created as follows: the winding of successive layers of tape onto a reel increases the radial compressive stresses in the wraps of tape at and near the hub. The continued inward radial deflection of the hub converts the circumferential tensile strain in the tape, originally caused by winding, to a compressive strain….The tape, hub, and winding parameters sufficient to obtain this condition can be determined using [the complex] analysis presented in Chapter 5. A highly compressible hub, high outer-wrap winding tension, low inner-wrap winding tension, the length of tape stored on a reel, and the entrapment of air during high-speed winding are strong contributors to low interlayer pressure

The interlayer pressure from winding is further reduced by temperature and humidity cycling and/or storage….The interlayer pressure can be reduced when the wound tape is subjected to a temperature of humidity change, and is dependent on the relative value of the coefficients of thermal and hygroscopic expansion of the hub and the tape. This effect is aggravated not only by the magnitude of this differential mismatch, but also by the mismatch in the tape’s radial and circumferential coefficients of thermal and hygroscopic expansion.

Bhushan also indicates that spoking can be triggered by impact forces to the tape reel. (Dropping it?)

One of the very interesting things which is discussed is that a tapered winding tension may produce a more archival tape pack than a constant tension winding tension. This raises many questions concerning current archival practices.

I suspect that more discussion of this will occur. Please leave your comments.

Peter Brothers left a lengthy response to this post in the Society of American Archivists list which I am reproducing here. I agree with him on all the major points, but I think Bhushan’s work was done in the late 1980s or early 1990s on single-reel data cartridges as part of the IBM proprietary tape systems like the 3480 (5.5-inch-square cartridge) and 3490 (same size as 3480). These are 1/2-inch wide serpentine recorded tapes and are the forerunner of the LTO tape.

=======================================

Date:      Tue, 15 Feb 2011 13:30:18 -0500
From:     Peter Brothers <peter (at)  specsbros (dot) com>
To:          Archives & Archivists (A&A) List <archives (at) forums (dot) archivists (dot) org>
Subject: RE: [archives] VHS Collections

Hello Richard:

I agree with you about not winding/rewinding tapes in storage unless there
is a compelling reason to do so. There is a significant chance of damaging
tape during the process. We wind and rewind tapes before transfer but that
is to check the tape condition, clean the tape for optimal signal response
and is done on special equipment.

In the Blog post you asked for comments, so here goes-

I can understand the findings you quoted from Bhushan as they might relate
to large reel-to reel tape. I was indicating in my earlier e-mail that
there are no studies I’ve seen that show a net benefit to periodically
exercising (winding) VHS tapes.

I don’t know what type of data tapes Bhushan was testing but if we compare
2″ video tapes (similar to the early data tapes we processed for the
government that exhibited the problems he highlights) to VHS, there are a
significant number of differences that make the conditions he was testing
much less relevant for VHS than for large reel-to-reel.

In the section you quoted from Bhushan’s study, he was suggesting exercising
tapes to counter the loosening of the tape pack due to tension stresses, hub
compression and expansion and contraction of the tape due to environmental
changes in storage. VHS is wound at a much lower tension than 2″ data tape
so that variations in the winding tension are not as critical to the tape
pack in storage. Similarly, some 2″ data tape we processed had rubber
wrapping around the hub that allowed for hub compression. This wrapping is
not used on VHS so hub compression is not critical. Finally, the main
problem we have seen with loose packs is due to expansion and contraction of
the tape that, as Bhushan points out, is due to heat and moisture changes in
the environment. The primary vector for thermal and hygroscopic
expansion/contraction is in the thickness of the tape. VHS is approximately
1/3 the thickness of 2″ data tape so there is significantly less material
per strand of tape to contract. In addition Bhushan indicates the
expansion/contraction effects are related to the circumference and radius of
the tape pack. A standard 120 minute VHS is 812 feet long and is on a 3 1/2
inch reel. A standard 60 minute 2″ video (similar to the 2″ data) is 4,950
feet long and is on a 12 1/2 inch reel. Considering the thickness, width
and length of the tape, there is nearly 72 times as much tape material on a
2″ 60 minute reel to be affected by expansion/contraction than on a 120
minute VHS and the 2″ reel is nearly 4 times the diameter of the VHS.
Expansion/contraction effects that might cause serious damage to 2″ tapes
are negligible on VHS.

Over the last 27+ years we have processed over 350,000 tapes at our facility
and we have definitely seen the negative effects of loose tape packs from
expansion/contraction during storage on large reel formats (2″ video, 1/4″
audio, etc.). Where these effects are extreme and allowed to remain
uncorrected, they can result in unrecoverable damage to the tape in
long-term storage. On the other hand, unless a tape has been exposed to
flood, fire or machine malfunction; we have never seen a VHS or other small
reel cassette with a hub lock that has suffered significantly from
expansion/contraction in storage.

All that being said, I do not believe there is any net benefit to
periodically winding and rewinding VHS tapes in storage. There may be some
benefit to exercising large format/large reel tapes but the practice, as you
pointed out, exposes the tapes to possible machine damage.

Peter Brothers
SPECS BROS., LLC
973-777-5055
peter (at)  specsbros (dot) com

=======================================

Doug Nishimura of the Image Permanence Institute of the Rochester Institute of Technology responded with a recollection of discussions “back in the day” concerning the issue of winding tape and stresses–this more from his experience working with film than tape, but some of the same basics should apply. I wanted to include the point about polymer flow as I do not think that Bhushan addressed that in the studies (but I could be wrong) and it presents yet another property of polymers to consider when deciding how to approach the issue.

I am still open to further discussions on this which can be appended here.

=======================================

Date:      Tue, 15 Feb 2011 14:52:18 -0500
From:     D NISHIMURA <dwnpph (at) rit (dot) edu>
To:          Archives & Archivists (A&A) List <archives (at) forums (dot) archivists (dot) org>
Subject: RE: [archives] VHS Collections

Back in the 1980s there was a rather circular concern (which came first?). If left alone, tape packs would loosen and therefore periodic winding was considered to be good to “retension” the pack and prevent damage due to a loose pack. I don’t recall ever looking for test data on the problem, but a number of tape manufacturers raised the issue. On the other side was polymer flow that said that if you put a polymer under constant stress, the polymer molecules will move (relative to each other) so as to remove the stress (and this is the problem that we have with films wound on small spools). (This is also known as creep or stress-relaxation in materials science, although technically, creep is more general and stress-relaxation applies to materials with constant strain and not constant load.) The demonstration was to hang a ribbon of some polymer by one end and hang a weight from the other end. If you left it over time, the ribbon would stretch and would get longer (under constant load.) So if you “retension” a tape and leave it, the polymer molecules should move relative to each other so as to remove the stress. In theory, the tape stretches and the tape pack gets loose again (requiring retentioning) and so and so on.

That then caused the whole question about whether it was better to leave the tape (and potentially cause damage to the tape) or retension periodically and risk destroying the magnetic information through tape stretching.

If you want to record on a tape recorder (and I do not recommend doing that these days as you’re just generating more tapes that will need to be transferred later) the first thing to do is get the playback correct.

1. CLEAN the machine.
2. If you haven’t done it in the last year or after a move (depending on the machine), demagnetize the heads and guides (using a strong demagnetizer like the Han-D-Mag).
3. Get a NEW (or trusted) calibration tape from MRL
4. The MRL tapes are supplied tails out. Rewind carefully and slowly onto a large-hub reel.
5. The first tone is a lineup tone, set for 0 on the VU meters of all channels.
6. If you are compulsive, the first time you do this, check the VU meter calibrations using an external AC voltmeter with wide frequency response. Most professional decks have very flat VU meters, so once you confirm that, you can just use the VU meters for the alignment.
7. There is a second lineup tone at different levels. If it is one of the -10 dB levels, take the machine out of playback cal and increase the level so that the meter again reads 0 VU.
8. On the 8 kHz azimuth section align the playback head azimuth (with an oscilloscope or a scope-application in the DAW) for minimum phase shift. Also check in mono sum.
9. Adjust the EQ trims (Trans-treble on the Studer A810/flashing treble light) for 0 VU.
10. On the 16 kHz tone, readjust the azimuth for minimum phase difference and maximum amplitude as above. Check in mono sum as well. It will never be perfectly stable.
11. Low frequency adjustment cannot be accurately accomplished off a test tape due to fringing unless the test tape and the play head track width is matched. However, one can often get close a test tape, but don’t necessarily tune for flat. It’s best to leave this alone if you can. The right channel of quarter-track machines will show more bass than the left as the fringing effect is coming in from both sides. Read the material on the MRL website.
12. Finally, recalibrate the playback level setting on the last tone. Leave the tape in a played wind on the reel it came on.

This completes the playback adjustment. Now you are ready for record adjustment.

1. Place a piece of blank tape on the machine (NOT your calibration tape from MRL)!
2. Record a 700 Hz tone at 0 VU on the meter when monitorin input and adjust the record level calibration for 0 VU when monitoring the output. Do this for all tracks.
3. Increase the frequency to 10 kHz (and drop it 10 dB at slower speeds, making up the gain in the uncal portion of the playback gain controls).
4. Decrease the bias level slightly so that you can find the peak. Then increase the bias past the peak until the 10 kHz level off the tape drops by the amount specified for that particular tape. It’s often somewhere around 3 dB. There are other, more precise ways to do this, but this should get you close.
5. Do a sweep of the high frequencies and adjust the HF record equalization for response closest to the response you got from the test tape. DO NOT try and improve the response from the test tape while adjusting record EQ as that will give you non-standard tapes.
6. Do a sweep of the low frequencies and then you can better adjust the PLAYBACK LF equalization.
7. Go back to 700 Hz and adjust for 0 on the VU meters when reading input.
8. Adjust record level control for 0 on the VU meters when reading output.

That should do it. I generally do a quick check flipping between input and output monitoring and you should hear no difference.

A word about levels. In the old days, I used to record at 185 nWb/m with Dolby A. With more modern tapes, 250 nWb/m will provide adequate headroom in most cases and may reduce the need for noise reduction processing. However, some have complained that 250 nWb/m is too low as it sounds too “digital” (i.e. “clean”). If you want to use tape as an effect, increase the record level to taste.

I really love recording with my Sound Devices 722 or somewhat less so with my MOTU 828 MKII, though there is nothing wrong with the MOTU that an RME FireFace 800 wouldn’t fix! Of course, now MOTU has the new 828 MKIII and it seems they have improved some of the things I complained about, but … twice burned (8Pre, also) … Anyway, I think that quality digital recording will capture sounds closer to the original than analog magnetic tape. This has been true in most tests run since the early days of digital recording and why most of the classical engineers who are looking for accuracy and not colouration were early adopters of digital. If you wish to record on analog that’s wonderful, but consider that analog tape is being used as much as an effect or sound-colourant as it is a storage medium. Also, remember that your legacy of tapes will be much more costly to preserve and migrate than digital files, although they may withstand neglect better.

Doug Pomeroy commented:

After aligning the deck for playback, per Richard\’s list, there is a simple way to set bias on any machine, recording on any tape. Use a 1000 Hz test signal and set bias current for maximum recording sensitivity (VU meter reading). Then for 15 and 30 ips recording, increase the bias until the
output level drops 0.2 dB. For 3.75 and 7.5 ips recording, decrease the bias until sensitivity drops 0.1 to 0.2 dB. One slight problem with this is being able, accurately, to read such small values on a conventional VU meter! (This method comes from Jay McKnight, of MRL Labs.)

Another method, also requiring a tone generator, is to record a low frequency, such as 30 Hz, at a very low level – at least 20 dB below normal operating level – and crank up the playback level enough to hear the output clearly, then adjust bias for the minimum amount of distortion (modulation noise, actually). This method allows one to easily adjust the bias by ear, listening for the cleanest reproduction of the low tone. The point of minimum modulation noise will very closely match bias settings arrived at by more elaborate means.

OF COURSE, after setting bias one must always go back and look at the high frequency response (10 kHz) and readjust the recording eq for flattest response.

Yes, bias setting is somewhat complicated, but it is good to remember it is always a matter of compromise, between the least distortion on the one hand, and the flattest overall high frequency response on the other.

Thanks for the comment, Doug. These are also good ways to set the bias. It is always a tradeoff. I no longer remember all the details, but biasing some old Magnetophonband Typ L from circa 1943 was a real challenge on a modern recorder as it is a homogeneous tape which means the \”magnetic coating\” is much thicker than on any coated tape, so the thickness loss is greater, and its basic sensitivity was far less than even something like 3M/Scotch 111.

]]> http://richardhess.com/notes/2008/02/02/aligning-a-tape-recorder/feed/ 0 http://richardhess.com/notes/2008/01/09/using-the-proper-toolsand-dont-try-this-at-home/ http://richardhess.com/notes/2008/01/09/using-the-proper-toolsand-dont-try-this-at-home/#comments Thu, 10 Jan 2008 03:10:08 +0000 Richard L. Hess http://richardhess.com/notes/2008/01/09/using-the-proper-toolsand-dont-try-this-at-home/ I didn’t think I needed to write this post, but it appears that someone purchased a Racal Store 4DS Instrumentation Recorder at least partially because I mentioned it, hoping that it would work as a four-track recorder for creating music.

Well, this is not a good idea. The machine uses non-standard-to-audio equalization. There is no “sel sync” (Ampex TM) to play back previously recorded tracks in time with newly recorded ones. There is no individual-channel erase system (and no erase head at all on the 7DS 1/2-inch, 7-track machine).

While this machine is useful to me for professional tape restoration. With a knowledge of its shortcomings and benefits, it can be a useful tool. I’m afraid, however, that I need to say, “DON’T TRY THIS AT HOME”!

In general, there are things that are posted on this Blog that if used inexpertly can fail to meet expectations and perhaps do damage. In this case, it only caused disappointment.

Specifically, instrumentation tape recorders were designed to gather data in the field and then permit later analysis of that data in the days before digital computers could do this much better. Audio and instrumentation look a lot alike, but are different enough that unless you completely understand the intiricate details, you will be disappointed.

I would also suggest that using the one-piece hard-disk-based digital music-production units from a variety of manufacturers will go much farther to enhancing your creative musical expression than an instrumentation recorder or even a cassette “porta studio”. I am not in a position to recommend any particular unit.

]]> http://richardhess.com/notes/2008/01/09/using-the-proper-toolsand-dont-try-this-at-home/feed/ 0 http://richardhess.com/notes/2007/11/21/how-to-play-4-track-1875-ins-tapes/ http://richardhess.com/notes/2007/11/21/how-to-play-4-track-1875-ins-tapes/#comments Wed, 21 Nov 2007 16:25:53 +0000 Richard L. Hess http://richardhess.com/notes/2007/11/21/how-to-play-4-track-1875-ins-tapes/ I received a query from a gentleman in Europe about 1.875 in/s 4-track tapes. He was frustrated in finding a good machine for transferring them. Apparently, they have many of these tapes. Here are my suggestions.

Perhaps the easiest answer is to find a Studer-Revox C274 with low speed options. They were made.

Two other options.  

(1) the Sony APR-5000 will go to 1.88 in/s by using its -50% varispeed. Most of the ones I’ve had do an adequate job at that speed, but I’ve been cautioned by the ex-Sony guys on my Sony APR mailing list that this is way outside of design spec. I use Nortronics in-line 4-track heads, but I’m also in the middle of building a staggered 1/3, 2/4 head assembly since that will improve inter-program crosstalk. None of these heads do really well due to gap length considerations. I suspect (I haven’t done the math) that you want a 50 micro-inch or shorter gap to do this well.

(2) The Racal Store 4DS instrumentation recorder which has constant-flux playback equalization (needs to be filtered in the computer afterward) and is not fantastic for S/N ratio actually goes to 15/16 in/s and is a 4-track machine. The previous two entries here feature this interesting machine. I did invest in three of them (the one in the pictures is the prettiest) as well as a 1/2-inch 7-track 7DS.

Someday, I might get a C274 logger…but I prefer adapting versatile transports to specific applications rather than collecting dedicated-per-format machines.

]]> http://richardhess.com/notes/2007/11/21/how-to-play-4-track-1875-ins-tapes/feed/ 0 http://richardhess.com/notes/2007/09/20/can-i-destroy-my-originals-after-i-digitize-them/ http://richardhess.com/notes/2007/09/20/can-i-destroy-my-originals-after-i-digitize-them/#comments Thu, 20 Sep 2007 20:36:45 +0000 Richard L. Hess http://richardhess.com/notes/2007/09/20/can-i-destroy-my-originals-after-i-digitize-them/ Jill Hurst-Wahl in her excellent blog “Digitization 101” asks this question and provides some good answers with reasons. You can read it here.

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