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:

90297, 91049, 91055, 91079 and 91149

The following were fine:

94132, 94133, 94298 and 96190

The reels that were bad did not squeal during playback, but left debris on the heads and guides that was just barely sticky, so these are obviously in the beginning stages of deterioration.

All of these were Ampex (pre-Quantegy) tapes purchased in the early 1990s. Batch 96190 have lighter grey boxes as opposed to the textured, darker grey background found on the earlier batches, and the reel labels appear to be silk screened, rather than having sticker labels. None of these reels have the old rainbow-style logo.

I would guess that the good batches will probably remain OK – they’ve had a good 17 years to go bad and would probably have done so by now if there was a problem.

For whatever it’s worth…

Gary Galo
Audio Engineer
SUNY Potsdam
…speaking for himself

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:

At the very top we can see a remnant of the left channel material, then the 120-Hz bars (62.5 mil spacing), then the remainder of the left channel material. In the middle is the guard band and at the bottom, the right channel.

Using a specially manufactured (by JRF Magnetics) assembly that contains a 4-channel 8-track head with a continuously variable height adjustment, we were able to lower the track one head to the middle of the good portion of the left channel. With that height positioning, track five’s head was well into the right channel, so we got a good transfer without the hum.

We believe this hum was written by the record head due to a malfunction in the recorder rather than an intentional erasure. If there had been an erasure, more of the left channel would have been erased and there would be a guard band between hum bars and the left channel audio as almost all erase heads were wider than the audio heads.

This type of damage is all too common using old consumer tape machines for playing tapes. I had an old junker machine in the 1960s that did this once to a tape. Unfortunately, it was also a quarter-track recording, so it was gone.

The magnetic record is fragile.

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.

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).

Not only was the tape cupping about its centre axis (with the basefilm shrinking so the edges were pulling back from the tape plane (away from the heads), it also had extremely wavy edges. In addition, the tapes would not lie flat on the reel due to the dimensional changes that were strongly embedded in the tapes.
We were able to play this tape on our stereo (NAB) A80, but discovered it was a 1/4 track tape (the original source had said it was half-track mono). We elected to stay with the A80 because:

• The A80 has the stabilizer roller which tends to “break the back” of cupping
• We had already adjusted the machine to have substantially higher tension to help flatten the tape–this was clearly a case of wanting the knobs to go to 11 or 12, but we had to settle for 10 on the play tensions.
• We do not have a four-track head for this machine AND the machines for which we have compatible heads do not have as easily adjustable tensions or the ability to safely set the tensions as high as we did on the A80
• The original recording was off-air AM radio after a trip of 1,000 miles through landline telco audio networks from 1964

So while the reproduction was only fair, we maintained good tape-to-head contact despite the inability to play this tape on other machines. If the content had been better fidelity and the client had been willing to pay for mounting a four-track head on the A80, we might have achieved some improved noise performance, but the original recording was quite low level (even correcting for the 1/4 track mismatch). Depending on segment, VU meter zero for the quarter track recording was somewhere around 15 nWb/m! We could hear recorded hiss,  however, over the tape noise even in this configuration!

We were able to improve listenability by using a filter that matched the playback bandwidth to the recorded bandwidth (it appeared to be about 200-3500 Hz, we filtered for 200-4000 Hz) and it sounded about as good as we would have expected hearing over a transistor radio in 1964. Further processing with Algorithmix Noise Free Pro reduced background noise (including random crowd noise, but not loud cheers–it was a football game) and made the announcers pop out more, so if someone is intent on listening to the details of what the announcers said, this would be easier to listen to, but less authentic to the sound of the original broadcast.

These tapes were transferred somewhere near their effective end-of-life. It would have been better if these tapes had been transferred 10-20 years ago. Based on other experience with Kodak tapes, I am not surprised with this. Interestingly, the Durol basefilm in its present state of decay was not translucent as most magnetic tapes are, so translucency of basefilm is not a 100% accurate test for acetate basefilm.

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Here are the ones with the picture of the chamber orchestra
http://www.richardhess.net/restoration_notes/111.jpg (red 7″)
http://www.richardhess.net/restoration_notes/120.jpg (orangy-brown 7″)
http://www.richardhess.net/restoration_notes/200.jpg (blue 7″)
http://www.richardhess.net/restoration_notes/311.jpg (grey-green 5″)

The moiré pattern you may see is the screening of the printing beating with your monitor.

These are earlier boxes for two if the above
http://www.richardhess.net/restoration_notes/111(A)_early.jpg
http://www.richardhess.net/restoration_notes/120(A)_early.jpg

And then it all became standardized in the 1970-era box
http://www.richardhess.net/restoration_notes/200_1970.jpg

When I get a chance, I’ll scan the box between the musicians one and the 1970s one.

Please remember that these modifications are provided “as is” and neither Andrew Pearson nor Richard L. Hess (owner of this site) can or will accept any responsibility for any damage, loss-of-use, or any other incident relating to this information. You may contact Andrew at    Andrew(dot)Pearson(at)bl(dot)uk

RE: Clock and other digital noise on the Studer A807

I managed to reduce the 9.6kHz contribution by moving a wiring loom from the capstan servo board away from the audio boards. I discovered that sliding the audio board assembley out past the capstan board caused the interference to pass from mainly channel 2 to channel 1, as that board became closer, and discovered the source of noise in the J1 connector – ‘M3-9600′ signal. I redirected the loom up towards the spooling motors and made about 9dB improvement, although in some cases the 28.798kHz became slightly worse. However, that’s much less objectionable than the audible whistle from the 9.6kHz.

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.

I asked the National Association of Broadcasters about their Cartridge, Cassette, and Reel tape standards as well as their Disc standard and they gave me permission to post these standards at my website.

These five standards plus some other articles of historic interest are available here in the history portion of this website. I hope that you find these of use in unraveling some of the challenges that old media present.

Here is the circuit diagram for the modification:

Use this at your own risk. If it doesn’t work, breaks a tape, or blows up the machine, I am not responsible. Please be careful, the +24V trace is under the likely area to add the parts.

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.

This monitoring topology is actually identical to two 1-inch 40-channel reel-to-reel logging machines I have where one can listen to any combination of one through forty tracks on a single output.

The solution for the reel machine is that I have about half figured out how to create 40 different outputs–and then I have to figure how to digitize 40 channels simultaneously. All can be overcome, but the cost to do it generally terminates the inquiry.

Fortunately, there is a solution for the 4-track cassette machines: use the higher-quality 4-track machines designed for music recording. I have a Tascam 234 (as well as a 238 8-track unit). Yes, I know these operate at 3-3/4 in/s while the logging recorders are running at 15/16 in/s (normal cassettes are in the middle at 1-7/8 in/s).

What I do is record the four tracks playing at 3-3/4 in/s into the computer at 88,200 samples/second (s/s). In samplitude, after the recording is made, I make a new virtual project that has a project sample rate of 44,100 s/s. I load the tracks into that. I then adjust all four tracks to -50% speed in the object properties panel. I use resampling for highest quality. This provides a 1/4-speed playback of the original files while maintaining a 44,100 s/s output file.

The digital data, of course, is actually at some point being processed at 22,050 s/s, placing the Nyquist frequency at 11,025 kHz, for an effective bandwidth of perhaps 10 kHz.

But, that isn’t a problem as only a very few Nakamichi cassette recorders ever made better than 10 kHz at 15/16 in/s — this wasn’t even officially in the Philips standard.

So, there you have a way to migrate these recordings into 44,100 ks/s WAV files while doing the bulk of the work in 4x real time.

You may add equalization and other filtering to improve the usually poor sound after the output is at the correct speed.

I actually had to put the recordings back on this infernal format after repair of the defect (very poor recording speed due to a broken machine), so I reversed the process with the Tascam 234 without adding any equalization and the client was apparently happy (I received payment and no feedback).
As an alternate to the speed/pitch adjustment in the virtual project, one could bounce the 88,200 s/s track played at 44,100 s/s to a second 88,200 s/s track and then repeat the process of loading that as a 44,100 s/s file and it will be in time. I prefer the single-pass approach that I can do in Samplitude.

One of the things that affects my procedure is that my audio interface (RME Multiface) does not work below 44,100 s/s.

Good 4-track recorders like the 234 have not been made for a while. Find them while you can.

In the early days, apparently wire recorders used bias as low as 30-40 kc, but Jay McKnight recalled in the pre-Ampex days, 60 kHz was common.

The Ampex Standard was 100 kc up to the MR-70.

With the MR-70, Ampex switched to 150 kHz bias frequency (and adopted the Hz) [Larry Miller, ex Ampex]

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.

Ampex AG-440 (A) stayed with 150 kHz [manual]
Ampex ATR-100 144 kHz erase, 432 kHz bias (1:3) [manual]

MCI JH-24 Multitrack 210 kHz bias, 105 kHz erase [manual via Brian Roth]

Otari MTR-10/12 II Bias 250 kHz (erase not spec’d) [manual]
Otari MTR-90 (original) 246 kHz bias, 123 kHz erase [manual via Brian Roth]

Sony APR-5000, APR-24 100 kHz erase, 400 kHz bias (1:4) [manual]

Studer A80VU 80 kHz erase, 240 kHz bias (1:3) [manual]
Studer A80 RC 150 kHz [manual]
Studer A810, A807, A820 2CH 153.6 kHz [manual]
Studer B67 150 kHz [manual]
ReVox A77 120 kHz [manual]
ReVox B77 150 kHz [manual]
ReVox PR99 150 kHz [manual]

Tascam 32/44-OB — 150kHz [manual via Tom Fine]

Technics 1500/1506/1520 — 120kHz [manual via Tom Fine]

Here is a quick sampling of published bias frequencies for two top-of-the line cassette recorders, a better-than-average portable, and an early compact portable.

Nakamichi Dragon (Along with the Nakamichi CR-7A, perhaps the finest machines ever made for overall audio quality) 105kHz (Service manual dated 1985 (scan) 1990 (copy))
Nakamichi MR-1 — 105kHz [manual via Tom Fine]

Studer A710 (a high-end cassette recorder, without the auto-azimuth that makes the Dragon superior) 150kHz (no date, scan on Studer ftp site)

Sony TC-D5M (a workhorse, good quality stereo portable) 85 kHz (Svc Manual dated 1980)
Sony TC-55 (an early compact — jacket pocket — mono portable) 41kHz (as low as I’ve ever seen) (Svc Manual dated 1972)

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/2008/01/07/magnetic-tape-splicing/ http://richardhess.com/notes/2008/01/07/magnetic-tape-splicing/#comments Mon, 07 Jan 2008 21:36:18 +0000 Richard L. Hess http://richardhess.com/notes/2008/01/07/magnetic-tape-splicing/ I received an email asking me to discuss tape splicing. Most of my work is now repairing old splices so I try and butt them together as best I can in an Edi-Tall block and use the blue Quantegy splicing tape (which will become harder to find with Quantegy exiting the business). I will not be evaluating a replacement for several years as I bought a large supply a few years ago.

I use paper leader tape as I’ve seen too many tapes damaged by the oxide adhering/laminating to plastic leader. I also don’t know where to get any more of this as I’ve laid in a large supply of this as well. Sorry.

Edi-Tall blocks are also out of production, sadly. They show up on eBay from time to time.

The splicing angle for new cuts is not all that important, but the angles were used to minimize disturbance and to provide a short crossfade at the splice (I used to hand-draw dovetail splices that were about an inch long to make the crossfade work in stereo).

The “MTA” or minimum track angle blocks for multi-track tapes were based on the speed of the tape and how much of a scatter was acceptable between the tracks as the splice rolled through.

Perhaps one of the hardest Edi-Tall blocks to find is the 0.150-inch one for cassette splicing and its use is really important for that application. There are blocks that look like Edi-Talls, but are not. Edi-Tall became a part of the Xedit corporation which has morphed into making ServoReelers for hanging microphones.

These blocks aren’t EdiTalls, but they are worth the price and are way better than nothing:
http://www.tapecenter.com/tapecare.html

While on the subject of tape splicing, here are few good Web links:
http://www.aes.org/aeshc/docs/3mtape/soundtalk/soundtalkbull26.pdf

http://www.ischool.utexas.edu/~smegison/Susan/Management%20e-portfolio%20iSchool%20projects/392L%20Intro%20to%20Audio%20Preservation/Tape%20repair%20and%20splicing%20paper%20and%20manual.doc

On January 16, 2008 Seb commented:

I use a ‘portable’ Studer-Revox Editing Cutter for my 1/4″ tapes that works perfectly !
You can find some similar editing block on players like B67…

I use an EMTEC 500 x 5,8 x 30 mm Splicing Tape Dispenser as tape splices. They are plastic-made, so the seem good for long-term resistance but, as I haven’t had the the opportunity to test it on a very long period yet, I don’t know how the glue which is used to manufacture them is evoluting.

I use mainly EMTEC, AGFA and BASF leader tape. They are matt and stretchable (not breakable) when strongly pulled, so I guess they should be Polyester or Mylar-made…

For the moment, I am completely satisfied by these products…
But any comments would be welcome !

Cheers,

Sebastien Vanhove,
Memnon Archiving Services,
Brussels, Belgium

]]> http://richardhess.com/notes/2008/01/07/magnetic-tape-splicing/feed/ 0 http://richardhess.com/notes/2007/11/26/rca-sound-tape-cartridge-and-quarter-track-reel-introduction-date/ http://richardhess.com/notes/2007/11/26/rca-sound-tape-cartridge-and-quarter-track-reel-introduction-date/#comments Mon, 26 Nov 2007 16:36:14 +0000 Richard L. Hess http://richardhess.com/notes/2007/11/26/rca-sound-tape-cartridge-introduction-date/ David Dintenfass kindly sent me an article from the October 1959 issue of Popular Electronics which says, in part, that RCA plans to have 65 titles in the stores in their new cartridges by Christmas 1959. Other manufacturers were shown to be making compatible players.

The article also heralded this as the saviour of tape, and talked about the “old” two-track format running at 7.5 in/s — the cartridges ran at 3.75 in/s (and on some models 1.88 in/s was also available). It goes on to say later that 7.5 in/s quarter track tapes are still a high-fidelity medium. The article referred to cartridges and quarter-track reels as the “one-two punch” against stereo records which seemed to take over from the two-track pre-recorded tapes. The open-reel tape at 7.5 in/s would be the “only choice for the quality-conscious stereophile” since the cartridges were only available in 3.75 in/s versions.

There was no mention of the later name “Sound Tape” in the article, but that appears to be the semi-official if not official name of this format. Thanks to Bill Schuh for that piece of information. Bill also provided a link to The Tape Place which specializes in out-of-print commercial tape releases. I have not used The Tape Place, so this is just being passed on, not a personal recommendation.

The Sound Tape cartridges used the standard 1/4-track interleaved format which prevailed for a decade as the consumer open-reel format.

Details about these formats can be found here and here in the Formats and Resources subset of this website.

 

]]> http://richardhess.com/notes/2007/11/26/rca-sound-tape-cartridge-and-quarter-track-reel-introduction-date/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/2007/11/19/studer-a80-covers-%e2%80%94-protection-and-more-work-area/ http://richardhess.com/notes/2007/11/19/studer-a80-covers-%e2%80%94-protection-and-more-work-area/#comments Tue, 20 Nov 2007 00:49:49 +0000 Richard L. Hess http://richardhess.com/notes/2007/11/19/studer-a80-covers-%e2%80%94-protection-and-more-work-area/ A simple, 5-sided box solves two problems:
   –Protection of the Studer A80
   –Providing more work surface

I have two Studer A80s that I use for high-quality master tape transfers. They are not equipped to handle the speeds and track formats found in most of my oral history work. As I delve into a large oral history project, I found I needed more work space, and didn’t have much room to store the A80s elsewhere.

I asked my handyman who helped me build the studio in 2005 to make me two A80 covers. We sketched them up and a few days later he brought them over. The exterior wrap-around is solid oak 1×6s. The top is 3/4 inch oak veneer plywood set in. Inside, there are 1×4 poplar strips running around that rest on the A80 frame and against the top. These were glued in and the glue holds the top in. Only the frame is screwed together. We opted not to bother hiding the screws. Presented as a hopefully creative solution as space utilization is always a challenge.

As to the Racal Store 4DS instrumentation recorder shown on top of this A80, please read this post:
http://richardhess.com/notes/2008/01/09/using-the-proper-toolsand-dont-try-this-at-home/

]]> http://richardhess.com/notes/2007/11/19/studer-a80-covers-%e2%80%94-protection-and-more-work-area/feed/ 0 http://richardhess.com/notes/2007/11/08/success-with-squealing-shamrock-031-tape/ http://richardhess.com/notes/2007/11/08/success-with-squealing-shamrock-031-tape/#comments Thu, 08 Nov 2007 20:06:08 +0000 Richard L. Hess http://richardhess.com/notes/2007/11/08/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).

 

Why did it work? — That is the big question. I suspect lower tape tensions than even the reduced-tension settings on the A810 and different head geometry were major factors, plus overall shorter unsupported tape spans, and few stationary objects contacting the heads, but there was still an erase and record head which had been removed from the A810. I think that the 4x speedup helped greatly. I also turned up the outside air (how I cool the studio in the winter–I like my fresh air this way–in the summer, of course, it’s connected to the central air conditioner) which kept the tape and recorder cool. I also think that the Racal Store 4DS doesn’t heat the tape and head assembly as much as most pro audio recorders do.

I received great support and wonderful ideas on both the Ampex and Studer mailing lists. Special thanks are due Jay McKnight who has been a supporter of speeding up the tape to eliminate squeal (which is really stick-slip and causes frequency modulation of the audio). I had avoided the 4x speedup on the A810 because of the signal electronics bandwidth limitations. While in this case, 20 kHz would work fine, I wanted to digitize with 40 kHz bandwidth to make sure I wasn’t losing any highs.

There may be room for misunderstanding as to the precise topology of the Racal Store 4DS tape path. Here is a brief explanation. The tape comes off the top of the supply reel and around the top-mounted tension sensor which is a roller. The tape then is unsupported from that roller until it enters the head area. The large diameter device at the top of the head area is merely a tape guide. It is both a “face” and “edge” guide both in and out and does not rotate. Next the tape passes the erase and record heads on the left side. The heads are on the outside facing the centre. Then the tape turns 180 degrees around the capstan motor’s soft capstan. The capstan also drives the mechanical footage counter. As the tape heads up, it passes the reproduce head and then encounters the tape guide on the other side. It then goes over the tension roller at the top and onto the takeup reel. The reel servos are interesting as they are fast and can drive the tape in either direction. This is useful since there is no pinch roller. The photo below shows a closeup of the head area.

 

As an aside: you can infer from the above picture that the complement of tape machines in my studio changes. The Studer A810s in the background are being set up to record full-track mono archival reels of some cassettes.

Before running out and purchasing one of these machines, please read this post:
http://richardhess.com/notes/2008/01/09/using-the-proper-toolsand-dont-try-this-at-home/

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