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Archival Services
Thank you very much for your interest in archiving your tapes. Your audio recordings are important to you, and Digital Atomics exists to help you restore your archives to the best possible condition on a format that will be around for the longest amount of time.
Digital Atomics can perform the archiving tasks for you, or consult with you so that you may archive your own tapes. Included are the explanations of both methods for your evaluation.
Because archiving of old or damaged material is a rather small market, many of the more sophisticated machines are built on a custom basis. Examples would be the air bearing analog tape transport, the multi-track-per-channel tape transport, and the vacuum system for removing moisture and restoring "sticky" tapes. If you have a large library to archive, then the cost of the machines amortized over a large number of tapes is quite reasonable.
There are some things that Digital Atomics needs to know about your library so that we can more intelligently advise you on the archiving process that best suits your particular requirements. We need to know the following:
Any information that you may have about the origin or history of the tapes will help in forming an accurate plan for the preservation of the material.
Below is a detailed explanation of the processes for Digital Atomics performing the archiving and consulting services where the client archives their own tapes. Look them over and we will help you determine the best path to preserve your audio library.
Digital Atomics Performs The Archiving:
Digital Atomics is very meticulous about the quality of their work. Every effort is made to insure that each tape is transferred to archival media at the highest possible resolution resulting in an archival copy that will be indistinguishable from the original.
Flow
Tapes can be shipped to Digital Atomics by the customer, or arrangements can be made for Digital Atomics or a bonded courier to pick up the tapes at the clients storage facility.
Hermetically sealed containers can be provided for shipping to maintain an unchanging environment for the tape. Atmospheric pressure and humidity are maintained until the containers arrive at Digital Atomics.
When the tapes arrive the tapes moisture content is measured to determine whether or not they need to be cycled through the vacuum decimation system. The vacuum system removes any accumulated moisture. We do not bake tapes to remove moisture because the baking process causes increased noise and harmonic distortion levels. The vacuum system also increases the available high frequency content of the tape.
When the moisture content has been stabilized, the next process is the determination of the tape brand, formulation, age, width, speed, equalization curve, noise reduction, number of tracks, track width and guard band between tracks. The correct head configuration is then chosen for the playback machine.
Depending on the condition of the tape, there are different options for
recovering the audio or video content:
Audio data is converted into the digital domain using multiple state-of-the-art converters of different resolutions. Proprietary computer software compares the results of the conversions and determines the best resolution for storage of the audio being archived. If the best quality is 24 bit, then the audio will be stored in 24 bit format as well as dithered 16 bit for easy access without requiring specialized equipment. If no additional resolution is obtained or necessary, then 16 bit storage will be the final format.
Video data is converted to digital at a resolution
that is at least that of the source video. Multiple resolution copies can
be made simultaneously so that the original only needs to be played
once.
Once in the digital domain, noise reduction, click removal, background
noise removal, equalization, or other forensic methods can be performed
as necessary.
The 24 bit audio is stored on CD-R, DVD-R, Blu-Ray, or LTO tape drives in both audio
and data format so that recovery or compilations can be done with the least
amount of production time.
All of the CD-R/DVD-R/Blu-Ray discs are verified with a checker (such as the Stage Tech
EC-2 for CD-R) to determine the surface condition and playback error rate
of the archive disc. Digital Atomics standards are 10 times more stringent
than Warner Brothers Records, or any of the CD manufacturing plants. A surface
error report is included in the booklet for each master disc.
If requested by the client, environmentally sealed containers are available for long term storage of the archived medium. Most clients request an archive copy and one or two copies that are available for access without disturbing the archive master. If the copy is lost or damaged, another accessible copy can then be made from the archive copy, which is then returned to its sealed container. Digital Atomics retains a copy of each project if requested by the client.
As each tape is archived, extensive documentation is kept as to the program
content and quality of the audio/video being transferred. This documentation
is included in the CD booklet for each CD. All data is compiled into
a master book and made available in database form for easy transfer to
the clients database system.
If requested by the client, Digital Atomics will keep on-hand an archive copy of the entire project in case of loss or damage to the clients archive copy.
Upon completion of the archival transfer, the digital archive master and the original tape supplied to Digital Atomics are returned to the client for storage in their facility.
Client Performs The Archiving:
Digital Atomics is very meticulous about the quality of their work. Every effort is made to insure that each tape is transferred to archival media at the highest possible resolution resulting in an archival copy that will be indistinguishable from the original. The Same concern for details is foremost in our consulting for clients who prefer to archive their own tapes.
Digital Atomics has worked on a consulting basis for Blue Thumb Records,
BMG Records, Sony Music, Polygram Records, Disney, and many private archives.
In these cases, Digital Atomics sets the standards and performance guidelines
with on going certification of the archiving procedure. This arrangement
assures that the quality of the last tape archived will be to the same
high standards as the first tape archived.
Every client's requirements are different. One company wanted to maintain archives on digital tape with storage in giant silos with robotics access to all stored tapes. Because of the limited life of tape based archives, automation was designed to have new copies made of every tape on a pre programmed interval.
Another client, with a more modest budget, stored all archived audio
on DVD-R and used a series of DVD juke boxes that held 200 DVDs each.
Any selection was available within 10 seconds. Because the predicted
life of DVD-R is more than 100 years, and the fact that DVDs are immune
to EMP (Electro Magnetic Pulse), made this storage method more desirable
to this particular client. Blu-Ray provides similar storage longevety.
In the role of consultant, Digital Atomics does not sell you any of the equipment. We put you in direct contact with the necessary manufacturers, or you may utilize your own sources to obtain the machines necessary for your needs.
Digital Atomics consulting service proceeds as follows:
Insure that the client is also properly archiving documentation that accompanied the original recordings.
If the client decides to undertake the archiving process themselves, then Digital Atomics wants to make sure that the final product is of sufficiently high quality to insure that the client has easy access to the audio content without bestowing any further damage on the original recordings. We also want to make sure that if there is a giant leap forward in storage technology, that the material can be transferred to the new media with NO generation loss, and that the transfers can be automated. This increases dramatically the longevity of the current investment in today's archival process.
Questions?
We all understand the need for preserving our recordings. There are a few special considerations that need to be addressed. They are:
1) Should the original tape be transferred to analog or digital?
All of the future release formats will be digital. I know that some people say
that analog sounds better than digital, but nobody disagrees that an analog
copy of an analog tape leads to generation loss. The copy is never going to
be as good as the original, period. A properly done digital transfer always
sounds truer to the original than an analog copy.
2) Does the tape need to be baked before I play it back?
There are tapes recorded during certain years that cannot be played back because
of tape damage. This usually shows up as a sticky tape that will not travel
through the machine. Until recently, the only way to temporarily correct the
problem was by placing the tape in a convection oven for a couple of hours at
125 degrees. This caused the absorbed moisture to leave the tape and the lubricants
to migrate back toward the surface of the tape. The tape could then be played
and would remain in this condition from several days to several months. If the
tape wouldn't play the next time, just bake it again. This is the way everybody
does it, except Digital Atomics.
Baking a tape places it in a hot environment. Haven't you noticed that all tape manufacturers state that you should keep your tapes in a cool, dry environment? This is not my definition of the inside of a convection oven. Most tapes from the problem period consist of a Mylar backing. Mylar shrinks when heated. At 125 degrees there is not enough shrinkage to notice with the naked eye. You don't put a 10 1/2 inch reel in the oven and get a 7 inch reel out when you are done, but there are dimensional changes that take place during the baking process. Using audio test gear you can measure the increase in harmonic distortion and the change in the playback frequency response of the tape. Every time you bake a tape, the harmonic distortion increases an average of 10%. The playback response change varies depending on the levels type of music recorded on the tape.
Digital Atomics has invented a new vacuum process that removes the moisture, makes the tape playable, and returns the frequency response of the tape to a state much closer to what was present when the tape was originally recorded. There is no degradation, only improvement in the condition of the tape.
3) Do I need to transfer my new 1/2" 30 ips masters? They are state-of-the-art!
Some artists and producers prefer the sound of analog tape for their mixes. That is just fine. A fact of life (due to the laws of physics) says that the sound on the tape will start to deteriorate from the time it is first recorded. A week after the recording, the sound quality will have diminished considerably. The older a piece of tape is, the more sound quality is lost. This is a logarithmic progression, so the greatest change in the quality of the sound will be near the beginning of the tapes life.
Luckily, the master tapes have gone through the mastering process, and have been transferred to digital domain for CD production. This was usually done very close to the time of the final mixing, so most of the information was saved, for a while. What wasn't transferred, though, was any alternate mixes, or tunes that were not included on the album but are being saved for the next release, or any of the TV mixes. Every time I have ever been in a mastering session where there has been previous material (mixed to analog) included in a new album, the producer or artist comments "The old stuff doesn't quite match up to the new mixes, can you do something?" The reason is generally not that the new mixes are that much better, it is because the old material has lost some of the sound quality over time.
4) I don't need to transfer my digital masters, do I? They're already digital.
There are some who think they don't have to worry about their digital tapes,
only the old analog tapes that have been sitting around for years. Every day
in a mastering room someone is having problems getting a Sony 1630 tape to play
back without errors. They twist the tracking control, play with the video levels,
try a different machine to get the tapes to play back correctly. At Digital
Atomics, we just transferred some Sony 3402 tapes for MCA Recoprds. The tapes
were recorded in 1992, so no problems were suspected. It turned out that there
were random errors throughout the tapes, and some of them had to be digitally
reconstructed in the computer.
Optical discs and CD-R are the safest format for digital audio. Digital tapes are subject to the same type of signal loss as analog tapes. Digital tapes have analog signals recorded on them. These signals are converted to digital information. Digital machines have error correction built in that can correct errors up to a certain point. Beyond that point, clicks and pops start becoming apparent.
Overview
Digital Atomics specializes in restoring both analog and digital tapes and storing them in an archival digital format. Digital tapes that exhibit errors during playback (1630 and DAT) should be transferred to a more robust medium. Analog tapes continue to deteriorate with time and should be transferred. Analog tapes can be transferred to high resolution digital in anticipation of the new DVD CD format.
Most record companies are not aware of the fact that if you re-master a digital tape (the original mixes) you are producing a 24 bit high resolution signal inside the mastering console, even if the original mix is only 16 bits. This high resolution version can be re-released in the new high resolution format.
Digital Atomics Exclusive Services:
Additional Services:
Rate Card
Prices:
Digital Atomics work is performed on an hourly basis. If a tape requires extra work to recover program material, then the extra work will be reflected in the total price. If,on the other hand, the tapes have been properly stored over the years and are very easy to archive, then the price for those items will be low.
If special equipment is required, such as special tape machines, vacuum, electron microscope, bifurcated head stacks, or chemical treatment, then these costs will be added to the invoice as additional charges. Any special needs will be brought to the attention of the client and discussed thoroughly beforehand.
Considering the fact that this is the last time that you will ever have to transfer your digital audio data, and that the data retention is more than 267 years, the cost for the satisfaction of knowing that your mixes will be there when you need them, is very modes
Media
Media Choices:
Archival services will transfer any format digital tape to archival storage media with a computer printout of the verified data integrity. Archival data will be written to one or more of the following formats:
Multitrack M-O discs and Phase Change Optical discs, which will retain data for 300 years. Analog and digital multitrack benefits from this storage media.
Storage Times:
Standards
Archival Standards:
Archival Standards? This should go right on the list of oxymorons next to Military Intelligence. Tape manufacturers have issued guidelines, such as "bake your tape for two hours at 125 degrees" or "the tape should be spooled off and on the reel approximately once per year", but there are no "standards" in existence.
Along with standard methods of conduct when it comes to caring for delicate tapes, you must also involve "common sense" in the practical application of those methods. Recently (Summer `95) Digital Atomics was involved in transferring masters for Blue Thumb Records. Some of the masters had very loud clicks scattered randomly throughout the program material.. The clicks were present on tapes from different studios, recorded in different years, and by different artists. As it turns out, the clicks were put on the tape by playing the tapes. At some point, prior to our transfer of the material, the tapes had been played or wound from one reel to another. During this process static electric charges built up on the tape. When the static discharged, it recorded clicks on the tape even though the machines were not in record. Now when tapes in that condition are transferred to digital, the clicks added will have to be digitally removed.
Before the tape is placed on a tape machine, determination should be made as to the condition of that tape. You are not supposed to see if the tape has dried out by counting the number of static sparks. You do not ascertain whether the tape is sticky by trying to play the tape at full tension while watching the machine come to a complete halt.
Whatever methods are decided upon for tape restoration and preservation, care should be taken not to damage the existing vehicle beyond its capability for recovery.
Digital Atomics Standards:
Digital Atomics has been researching methods of archival audio storage for 15 years. We have been working with major record labels, equipment manufacturers, media manufacturing companies, music publishers, and divisions of the US government to come up with methods of storing audio information that will last well into the next century.
Record labels and their insurance carriers have proposed that an independent third party set the standards for archival practices. A common denominator among record companies would lower the cost of media and equipment by increasing the production volume of those systems necessary to maintain an efficient archive. We have been in close contact with mastering facilities around the world to come up with a delivery medium that will allow each mastering facility to produce the archival copy of the completed album project at the time of final mastering, thus eliminating an additional step after delivery of the final mastered product to the record company. Producing the archival copy of the project at the mastering facility allows for higher quality, because at this stage the archival media can be produced at 20 bit or 24 bit resolution. If the archival copy is made after the CD master is turned over to the record company, the higher resolution is no longer possible.
Digital Atomics has been involved with Rane Corporation in the development of the PaqRat, a box that will allow high resolution audio storage on an inexpensive DA-88 or ADAT tape for delivering high resolution mixes to the mastering house.
We have been working with Kodak concerning CD-R media for long term storage. As of today, Kodak CD-Rs will last over 200 years. If you transfer old analog tapes to CD using 20 bit converters and Super Bit Map or UV-22 processes, you can be ensured that you won't need to make transfers again for a very long time.
Digital Atomics has applied for patents dealing with the process of transferring analog tapes at half speed to CD-R, thus improving transient response and overall fidelity. Half speed transfers also insure less damage to the original master. We are also working on imaging technology for transferring old cracked lacquer disks to digital without contacting the grooves on the original disk.
Digital Atomics, in close association with Music Sciences Corp, has developed a Rubidium Plasma Atomic Clock. This clock delivers Word Clock for digital transfers that is accurate to within one second over 10,000 years. The reason for a timebase this accurate is for frequency stability and low jitter. It is now widely known that jitter in the time domain can lower the quality of analog to digital transfers. A clock jitter of less than one picosecond is by all intents, perfect. Digital Atomics is setting the standards by which other methods will be compared.
Multitrack tape transfers have been at a disadvantage until now. The only possible storage medium for multitrack tapes has been digital multitrack tapes. There has been no archival quality media for multitrack storage. Digital Atomics has been working with a major equipment manufacturer to produce a format for multitrack archival. We have produced a machine that will record 24 tracks on Magneto-Optical discs. The data retention is 99% over 300 years. This is the format we use for archiving multitrack tapes, as well as 6 and 8 channel mag tracks for film sound archiving. This standard is quickly being adopted by major record labels, movie studios and theme parks.
Digital Atomics is working closely with insuring organizations to provide standards that will stand up in court. An artist's master tapescan be preserved at a level deserving of "unique and irreplaceable" artistic material. This form of protection becomes much harder when each record company has its own idea of how to archive priceless masters.
Documentation is also of great importance when it comes to preserving the past. All documentation associated with a master recovery project, from box covers to label copy and album cover artwork, is scanned and provided on CD-ROM. (Automated high resolution scanners exist that will scan in excess of 10,000 pages per day without user intervention). It is also possible to include low resolution audio (thumbnails) of the archived material for search reference. When there are sometimes as many as ten or more different versions of the same song by the same artist, hearing a little piece of it can save a lot of time digging up the wrong tape.
Data from each archived tape, such as the date of initial recording, studio, musicians, condition of tape, quality of audio recovered, and 25 other parameters are stored in a database in accordance with the NARAS Archive Database Standard format for inclusion in the National Archives Database.
As new technologies emerge, Digital Atomics will update our clients, keeping them abreast of the latest archival methods. Some of these improvements may include High Density CDs (DVD), 24 bit A/D converters, 96 kHz sample rates, frequency shift data layering for high density storage requirements, and Data Streaming for Very High Resolution professional audio storage.
Digital Atomics is working with music publishing companies to provide database retrieval systems that would allow instant recall to any song in the entire catalog through the use of CD-R and CD changer technology.
Digital Atomics is producing the definitive white paper on the best way to preserve future product and reclaim masters from the past. This paper will be the "Owners Manual" for any archiving endeavor.
The Facts
Tape Library Fears Become Reality.
· Your fortune is tied up in digital master tapes that don't play back any more. A big movie producer wants to use a cut that was recorded on a digital machine that no longer exists.
· An important artist wants to know if you are taking care of his master tapes.
· You have alternate mixes of hit songs that were not part of the US release and were only stored on DAT tapes. You realize that these mixes may add value to foreign releases.
· Your analog tapes are starting to turn green and wrinkle. You are afraid to transfer them because they may fall apart during the transfer.
· CD production is an inexpensive way to add income to re-released masters. Even if they are scheduled for release years in the future, now is the time to transfer analog and digital tapes, while you still can. Analog tapes transferred now into 20 bit formats can be re-released in the new DVD format.
Analog Tape Facts:
Half Speed Mastering
Before the Compact Disc, many mastering facilities offered half speed mastering. Cutting lathes were modified to cut the lacquer master at 16 2/3 rpm while the master tape was played back at half of it's originally recorded speed. This produced better high frequency transients in the master that was used to produce the records. With the dawning of the Compact Disc, it was no longer possible to play back the analog tapes at half speed because it was not possible for the digital machines to record at half speed: The end of half speed mastering (until now).
A positive side effect of half speed transfer of old analog tapes is that the delicate master is traveling at only half speed over all of the mechanical components of the playback machine. The tension on the tape is less because lower speeds require less pressure against the playback heads. The bending of the tape over the tape guides happens more slowly allowing the oxide coating and the mylar base to bend together. This more delicate approach during the transfer process protects the master from further damage.
Another well known method of recovering transient material in analog masters is to make the transfers backwards. Because of the way analog tape works, the leading edges of the transients are smeared as they are recorded on tape. If you play the tape backwards the smearing in the opposite direction tends to recover more accurately the original attack of the instruments. In the case of making an analog to analog transfer, the copy was now backwards. When this tape was played in the reverse direction, the music was again frontwards and greatly improved in the transient department.
For the first time, analog masters can now be archived to digital BACKWARDS at HALF SPEED using state-of-the-art 20 bit converters and custom designed sample rate conversion systems. The archived recording is delivered to the client on 267 year guaranteed CDs in 16 bit format utilizing Apogee UV-22 or Sony Super Bit Mapping technology to give better than 16 bit performance from 16 bit media. The client may elect to additionally receive a copy on 24 bit digital media such as Sony PCM-9000 optical disc or Paq Rat format on Sony PCM-800 (8 track digital) tapes.
Removing Moisture
Baking tapes is not the answer. Mylar that is used as a backing material for most modern recording tape is made by stretching the Mylar to obtain the correct thickness. Mylar has a memory. At temperatures above room temperature, Mylar starts to return to its original shape. This shrinkage distorts the physical properties of the tape and the audio information stored on it. If a tape is baked in a convection oven to remove the moisture, then the tape is being damaged and the elevated temperatures further degrade the magnetic signal recorded on the tape. A baked tape can only be played back a few times before it is totally useless and must be discarded.
There are chemicals that will reconstitute the binders in the tape, but they have an adverse effect on the mylar backing that supports the recording medium. After chemical treatment, the tape may or may not be succesfully played back once.
At Digital Atomics, we have constructed a vacuum desiccator to remove the moisture from the tape without damage to the tape or further loss of recorded material. Recovery using this method is virtually 100%. This method works with all sizes of analog tape, digital audio tape, and video tape.
Multitrack Archiving
Multitrack tapes have some special considerations. Digital Atomics has the only multitrack M-O recorder that can sucessfully produce archival quality storage for these formats.
Mag film soundtracks can also be archived to 8 track M-O drives. These drives can be SMPTE synchronized for later transfer or re-mixing.
Analog Tape Formats:
Analog recordings come in many different track formats recorded on many different types of media. Even back in the days of wax cylinders, you had a choice of two minute or four minute formats. A two minute machine could not play back a four minute cylinder. Ever since then, it has been a format nightmare.
Formats that have come and gone include:
Analog Recovery:
The first erasable recordings were done on magnetic wire. Early tape used paper as the backing material. Some of the best quality early recordings were done optically on film. After paper backing came Acetate. Acetate is also used for mag film stock. Mylar replaced Acetate in the recording studio, but Acetate is still the backing of choice in the film industry. All of the different backings use a binder, or glue, to hold the oxide material for the magnetic recording process.
As tape ages, the binder attracts moisture from the surrounding environment. This moisture makes the binder "ooze" or become sticky. This sticky property makes it almost impossible to play back the tape because the tape sticks to all of the guides and tape heads that it passes. The only way to play back the damaged tape is to remove the moisture. The moisture can be removed by baking the tape, running it through a chemical bath, or placing it in a very high vacuum.
The magnetic oxide on the tape is not a permanent storage vehicle for the magnetic information. The information can be erased easily by recording over it. The information recorded on the tape also looses some of its quality over time. An analogy would be like writing on newspaper with a fountain pen. The ink spreads out so as to make the writing less legible. The same thing happens in an analog recording. The magnetized particles in one area of the tape change the magnetic properties of nearby magnetized particles. You can most easily notice "print through" which records the sound from one layer of tape onto an adjacent layer of tape. The same thing happens to the magnetic particles located nearby on the same layer of tape. This manifests itself as distortion and reduced high frequency response during playback. The higher the recorded level on tape, the more this phenomenon will effect your recording.
One more variable that can effect how well an analog tape is recovered is the design of the heads that recorded the original tape. The most important of the design parameters is the track width and guard band ( the space between the tracks). Playing back the tape on the proper head stack can make a significant difference in the quality of the recovery.
Time Base Accuracy
Time base accuracy is of high importance when transferring material from analog to digital formats. We use a Rubidium Plasma Atomic Clock for timing accuracy. When we transfer a tape to digital at 44.1kHz, it is EXACTLY 44.100000000kHz. When sample rate conversion is done from 48kHz to 44.1kHz, a super accurate clock means more accurate math during the conversion resulting in less noise and harmonic distortion products added to the signal. With jitter specs in the >1 picosecond range, 16 bit transfers cna sound as good as most 20 bit transfers. 20 bit transfers with low jitter are unbelievably transparent and hi-fi.
Digital Tape Facts:
Many companies transferred their catalogs of analog tapes to digital many years ago. I transferred the Steely Dan analog masters to 3M digital format in 1981. By transferring the tapes early in the "digital age", any further analog deterioration was halted. More recently the early 3M tapes were transferred to CD. The 3M tapes were marginal in their ability to play back correctly and finding a machine to play them back was a task in itself. Because the data was digital, it was possible to recover the albums completely with no further degradation during the additional 14 years of storage.
Digital storage technology has come a long way in the last 15 years. Future sighted companies who transferred their masters years ago are ahead of the game. If you transferred an analog tape to digital 10 or 15 years ago and played them both back today, the digital would sound much better because of the additional analog deterioration. The problem now is that early digital tapes are not playing back as well as they should be. Digital formats such as Sony 1610 and 1630, Mitsubishi X-80 and X-86, Sony 3402, 3M 4 track, Soundstream, JVC, Sony F-1, and now DAT tapes are failing to play back as well as they did years ago when the tapes were recorded.
The biggest problem is that the information is stored on magnetic tape. Magnetic digital tape is subject to the same problems as analog tape. Temperature, humidity, magnetic fields, and shock from handling can reduce the ability of a tape to play back its contents. The lack of availability of the correct playback machine does not help matters. We have seen cases where tapes left at a studio were actually recorded over because of blank tape shortage. The answer to this problem is to archive digital audio on to CDs which are absolutely not erasable, or to optical media which are immune to electromagnetic fields. Placing an optical disc near a speaker or electric motor, or passing it through an x-ray machine does not erase the data stored on it.
Digital Tech Talk:
Here is a little more explanation of what usually happens to a digital tape that makes recovery difficult.
The F-1 format:
F-1 format tapes actually cover a variety of different systems. The format was originally the EIAJ format for consumer digital audio. The format is specified to be 14 bit. There were machines available from Technics and other manufacturers that included the digital processing and a VHS format video transport in a single unit. The audio was recorded as a video signal consisting of little black and white dots that, when played back, were turned back into digital information and exited the machine as audio.
Soon after came the Sony F-1 with a modified version of the EIAJ format. There was a switch that let you decide whether you wanted to record 14 bit or 16 bit. Everyone who owned a Sony F-1 selected 16 bit. The problem with selecting 16 bit was that the extra bits were recorded in an area that was used for error correction data in the 14 bit mode. If you recorded 16 bit, then you were more likely to encounter un-correctable errors. There was a unit produced by Sony for Nakamichi called the DMP-100. Some capacitors were different and the outside was black instead of silver. Otherwise it was a Sony F-1. Sony also produced the PCM-501, PCM-701 and PCM-601 (with digital inputs and outputs). The tapes produced were identical.
F-1 Problem Number One- Beta-VHS Wars:
Some people who recorded using the F-1 format decided that since VHS was a better video format than Betamax, that the digital audio recording would be better when stored on VHS tape. The reality of the situation is that they basically shot themselves in the foot. All Beta machines have a switch on the machine labeled "PCM". When PCM was selected, the video drop-out-compensator was disabled, allowing the F-1 processor to perform the error correction necessary to recover the digital audio. If the switch was not in this position, then the video deck would perform video type error correction which would increase the digital audio errors by about ten times. This would cause quite a few un-correctable errors resulting in poor digital audio recovery. VHS machines do not have a switch that allows you to disable the drop-out-compensator. Without using a specially modified VHS transport, the error rate will easily be above the threshold for correctability.
F-1 Problem Number Two- Emphasis:
Un-modified F-1 (all types) processors operated with "emphasis" added to the digital audio signal. Emphasis was some engineers bright idea that if you emphasized the high frequencies during the recording and then reduced them during playback, that you would have a quieter recording. Not true. By employing emphasis, you usually had to record at a lower level thus negating any apparent noise reduction due to the emphasis. Sony 1610 and Sony 1630 recorders have the ability to record with emphasis also, and the earliest CDs were produced with emphasis turned on. It was later learned that it was best to record without emphasis. No CDs made today have emphasis (unless by accident). There were some F-1 processors that were modified to record with no emphasis. This fact was usually not marked on the tape box.
F-1 Problem Number Three-Wrong Sample Rate:
Because the F-1 processors were designed to use standard video decks as the storage medium, they were designed to produce the video image at the standard video frame rate. In the US this is 29.97 frames per second. This meant that the sample rate was not really 44.1kHz, but actually 44.056kHz. F-1 processors designed for PAL and SECAM format video were actually 44.1kHz.
Some F-1 users modified their F-1 boxes to actually record at 44.1kHz. This was easily done by replacing the main clock crystal in the US versions with the crystal used in the PAL/SECAM units. US video machines have enough tolerance so that they will run a little fast to keep up with the frame rate during record. The fly in the ointment here is that when a consumer video deck is in play, it uses the crystal built into the video deck. The audio that was recorded at 44.1kHz is now playing back slow, at 44.056kHz. The only way to play back the signal properly is to use a professional video deck that will accept an external reference for playback. This deck can be sped up to 30 frames per second to play back the audio at 44.1kHz.
F-1 Problem Number Four- Time Shared Converters:
The F-1 series of processors used one A/D converter and one D/A converter to process both channels. The converters would sample one channel and then sample the other channel. This meant that there was a half sample delay between the left and right channels. The exact same thing happened during playback, so there was no big deal. When F-1 tapes were transferred digitally to Sony 1610 or 1630 format for CD production, there was a phase discrepancy between the two channels because the Sony 1630 (the standard for CD masters) processes both channels simultaneously.
F-1 Problem Number Five- DC Offset:
This problem is lumped in here with the other F-1 problems, but it also affects tapes produced by Soundstream, Sony 1610, Mitsubishi X-80, 3M 4 track, and other early digital machines. The problem is DC voltages present on the digital tape. The DC voltages are necessary to make the analog to digital converters perform their job better. The DC voltage, or offset as it is called, lowers the zero-crossing (low level) noise in digital recordings. Some digital machines required a relatively high offset voltage to make the converters sound good. The Soundstream machine was one of the worst.
This DC offset caused pops and clicks at the beginning of a CD, or when you skip to another track. If there was an edit performed between two takes with different offsets, there would also be a click. If the DC level was high enough, and you had the volume turned up, the thump could damage the speakers. It was decided that every effort should be taken to remove DC offset voltages from CDs. The DAT standard specifies that there will be no DC recorded on tape. Any DC used in the conversion process should be removed before the digital audio is stored on tape. Current Sony 1630 processors, as well as other digital formats, adhere to that requirement.
Sample Rate Problems:
Early in the digital wars, there was no sample rate standard, except for the CD specification of 44.1kHz. The professional machines could be whatever they wanted to be. The Mitsubishi X-80 was 50.4kHz. The first two X-80 machines were owned by George Duke and myself. Our machines were used on many projects besides our own, and turned out many 50.4kHz tapes before everyone decided on 48kHz as the professional sample rate..
The 3M Digital Mastering System consisted of a 32 track machine and a 4 track machine. The 4 track machine was used to perform edits, and to store the final master during mixing and mastering. The 3M sample rate was 50kHz. Later, there was a modification available that allowed the machines to be switched between 50kHz, 48kHz, and 44.1kHz. Not many people purchased this modification, and to remain compatible with other 3M machines, almost every 3M user stayed with the 50kHz sample rate.
We have already talked a little about tapes that were recorded at 44.056kHz. This was not just an F-1 problem, it also crept up whenever a project was referenced to video. Until recently, any recording done while synched to video was "pulled down" to the video rate of 44.056 kHz or 47.952 kHz. Yet another sample rate nightmare.
Tape On Wrong Machine Problem:
If you don't read the labels on a tape box, one tape can look pretty much like any other. A Sony 1630 tape looks like a 3/4 inch video tape because it is a 3/4 inch video tape. Because of the nature of the data stored on 1630 tapes, trying to play one on a regular video machine can cause plenty of problems. Wrong tensions, dirty heads, maladjusted tape paths, or any number of other problems can damage a tape so that it can't be recovered without a lot of work. The same is true of VHS and Beta format digital audio tapes. One pass on the wrong machine can spell disaster.
3M 4 track tapes are 1/2 inch wide. I have personally seen a 3M 4 track tape placed on an analog 1/2 inch machine. When the tape wouldn't play, the machine operator fast forwarded to another spot on the tape. It wouldn't play there either, so the tape was rewound and placed back in its box. The damage was done. The tape would never again play back properly on the correct digital machine. The same thing has happened with 1/4 inch digital tapes.
Digital tape is much thinner than analog tape. The reasons for using thinner tape are better head contact and longer playing time. Because the tape is recorded with digital information, there is no "print-through" as there is with analog recording. Usually digital machines require higher recording speeds to record the digital information on tape. The 3M machines record at 45 inches per second. Digital machines are designed to transport thinner tape, so the tape is wound on the reels properly during fast forward and rewind. Analog tape transports are not set up to handle the thinner tape, so when thin tape is used, the wrap on the reels is very ragged and the edges of the tape are wrinkled. This is not a good thing for digital tape. Excess errors will show up when the tape is played on the digital machine. Digital tape is easily stretched or broken when wound on an analog machine.
Wrong Splicing Tape Problem:
Some digital machines allow you to edit the tape with a razor blade. The Mitsubishi X-80 was the most common for razor blade editing of digital audio. There have been edits performed on the 32 track Mitsubishi X-800 series, as well as the Sony 3324 24 track machine. The edits had to be very precise, and no residue from finger prints or other contaminants were allowed.
In analog editing, the tape is cut at an angle, the pieces are butted together so as to leave no gap, and a piece of audio splicing tape is used to secure the edited pieces. When editing digital tape, the cut must be vertical and a small gap, about the width of a razor blade, must be left so that the digital machine can detect the edit. In addition, the splicing tape used must be "digital" splicing tape. Digital splicing tape is different from analog splicing tape. First of all, digital splicing tape is thinner and more pliable to allow proper head contact at the edit point, and because the tape being spliced is so thin. Second, the adhesive is different on digital splicing tape. Because there is a gap left at the edit point, a small amount of the adhesive shows through the splice. This adhesive spot comes in contact with the head as it passes during playback. The adhesive cures so it does not leave behind any residue. Any residue that got on the oxide face of the digital tape would cause tons of errors. Not what is needed for a good digital edit.
The reason I bring this up, is that almost half of the edits I have ever run across on digital tapes were done with analog splicing tape. The edit may have played back right after it was performed, and maybe even for the next few weeks, but after the tape has sat around for awhile, the adhesive has crept through the gap at the edit point, and the next time the tape is played, the adhesive will transfer to the heads and guide rollers of the digital machine and then transfer gunk for up to ten seconds on either side of the edit. The error lights will come on like the lighting of the White House Christmas Tree.
DAT Machine Alignment:
DAT tape machines have been a boon to the digital industry. For the first time, the producers could take home a digital tape to listen back to mixes. DAT machines were much cheaper than $20,000 reel to reel digital machines for mixing to, so many record masters only existed on DAT tape. DAT tape was designed as a consumer format, and as such, does not have all of the extra protection that may have been deemed necessary for professional use.
DAT machines are not all aligned to the exact center of the allowable tolerance for DAT transports and head alignment. It happens all the time that a DAT tape that plays back perfectly on one machine, will play back poorly on another machine. If there is a transport problem with the record machine, the chances are even less that the tape will play back 100 percent on another machine.
DAT Tape Quality:
DAT tape quality range is unbelievable. Some tapes I have run across would not make it through the machine once. Part of the tape problem is actually problems with the shell that contains the tape. If the shell binds the tape at all while you are recording, then chances are that the tape will not play back properly. Sometimes the tape and shell are fine initially, but warpage of the shell at a later time makes playback almost impossible.
DAT Pause Editing:
This problem rears its ugly head when the artist or producer tries to perform edits by using two DAT machines. The record machine is placed in PAUSE-RECORD, and at the proper moment for the edit, the deck is taken out of PAUSE to record the continuation of the edit. When the DAT tape is played back, the edit is perfect. This also happens when an album project is assembled into the proper sequence by copying from one DAT machine to another. The proper spacing between tunes is accomplished by using this same PAUSE editing technique. Everything plays back just fine on the original machine. When the tape is played back later on a different machine, the beginning of each tune sounds like part of it is missing. Well, it is missing. Because the alignments of the record machine and the playback machine are not identical, the play machine cannot track correctly over the PAUSE edit and the machine mutes for a split second. By the time the playback machine has recovered from the error, part of the start of the song is missing.
DAT Hard Disk Transfers:
Problem number four is a result of transferring digital audio from a hard disk editing system to a DAT tape. It is not the transfer of digital audio information that causes the problem, it is a combination of errors on the part of the operator of the hard disk editor and a problem with some early DAT machines. Some DAT machines look at an incoming "sample rate flag" and record that flag on the DAT tape. That flag is used by the DAT machine for playback speed. Other machines actually look at the sample rate coming in to the DAT machine to decide what flag to record along with the digital audio information. It is possible to record something at 48kHz but have the flag on the tape set for 44.1kHz. In some hard disk editing systems is it possible to have the flag set one way and the sample rate set the other way. When you go to play back the DAT tape, some DAT machines will play back one way, some will play back the other way, and some will simply mute or stop the transport because of an illegal combination. There were some machines that when faced with an incoming signal like this, would act like they were recording, show the digital audio on the meters and send the audio out the analog outputs, but when you went to play the tape back, it would be blank. If you just made the copy without listening back to it, you would never believe that the tape was blank.
DAT and Emphasis:
One final DAT problem. Some early DAT machines, such as the Luxman, recorded with emphasis on. DAT tapes that were transferred digitally from F-1 tapes would also contain emphasis. Some transfer boxes, such as those used to transfer digitally from ADAT 8 track machines and some sample rate converters, turn off the emphasis flag, but the tape still contains emphasis. This causes the tape to sound unusually bright on playback. This problem needs to be remedied during the transfer.
The Final Recovery Difficulty:
If all else fails, this one will make sure that you can't recover your mixes. You can't find the right machine to play it back on. The 3M machines were only made for a short period of time, and they are getting harder and harder to find. Finding parts for them is not easy either, as 3M no longer supports them.
Mitsubishi has discontinued the X-80 and X-86 two track machines, the X-800, X-850, and X-880 32 track PD format machines. Otari was building PD format machines, and will at this time (end of 1994) only custom build a machine after the sale. Otari did not make a two track reel to reel digital machine.
The only current digital multitrack format is DASH. This is supported by Sony with the 3324-S 24 track machine and by both Sony and Studer with 48 track machines. Tascam produced a DASH format 24 track which is no longer made, but the tapes will play back on any other DASH format machine.
Sony has discontinued the 3402 reel to reel 1/4 inch digital machine. Sony has discontinued the 1630 format. Sony is trying to replace the 1630 video tape based format with the PCM 9000 optical disk format.
F-1 format machines disappeared with the introduction of the DAT machine in about 1987. The Beta format of video machine used to store the digital audio information has also been discontinued for almost ten years.
The Akai ADAM, 12 track digital on Hi-8 video tape, was discontinued shortly after the ADAT format was introduced. The Akai MG-1212 12 track analog format is no longer manufactured either.
Why Not Backup to Analog?:
For the same reason that you don't keep color Xerox copies of $100 dollar bills in your safe deposit box. It might look good, but try using it for anything.
Artist and producers have clashed with their record companies for accidentaly using analog tape copies of digital masters to produce CDs. Phil Ramone, Diana Ross, Blondie, Steely Dan, Billy Joel, and many others made the record companies destroy the bogus CDs and do them over again with the correct master tape. How do you think they would feel if they thought the record companies were archiving their million dollar masters on analog tape that is going to start deteriorating the second it is recorded. When the analog tape starts to sound bad after a few years what do you do? Copy it to yet another piece of analog tape so that the master is yet another generation down? The sound quality will not improve when copied to a new piece of analog tape. It is true that a bad analog tape will play back, but it will play back badly. It is like trying to receive a television broadcast from 100 miles away with just the built-in rabbit ear antenna. One major record company had to apologize publicly in Billboard for using an analog tape copy for CD production instead of the digital masters. It was an embarassing situation.
It doesn't matter what brand or type of analog tape you use, there is still a generation loss, and it degrades the sound of the master. With new masters being produced on digital 48 track machines and mixed on consoles like the AT&T Disq system, it is a major slap in the face to artists and producers to even think about archiving to analog tape.
Backup to CD-R or M-O:
We have discussed all of the problems with different forms of digital tape storage. Remember that these have been tape based systems. When digital was introduced, tape was the only possible way to store the data. As technology has advanced, optical disks, and now recordable Cds have proved to be much more robust in the retention of digital data.
We have mentioned also that there has been a problem in obtaining the correct machines to play back some of the digital formats. When your master is archived to Kodak CD-R, the media has not only been tested and found to last more than 267 years, but these CDs will play back on any consumer CD player. You do not need any special professional player to retrieve your data. Professional players will play back CDs with better quality and error correction, but with millions upon millions of CD players available, there will never again be the problem of finding a machine for playback.
The defense department backs up all of their data to CD, and has ascertained that CD is the best format for retaining digital data. Even with major scratches on the surface of the CD, the data can be recovered 100%.
The multitrack option is to transfer to Magneto Optical disc. This format has improved to the point where data retention is 99% after 300 years. This gives the same amount of data retention to your multitrack tapes as you have on CD-R with your two track masters.
What to Transfer From:
When sending tapes for transfer, the more documentation available, the better. If, for instance, there is a box full of tapes that came from a particular album project and one of the tapes is marked different from all of the rest, then there are two possibilities. One is that the tape is different, and the other is that it is marked wrong. If the tape you want transferred is the one that is different, then send one or two of the other tapes for comparison. It will then be easy to tell whether the markings are correct or not.
If there is more than one format available from the sessions in question, send all of the formats. It is possible that information that cannot be recovered from one can be transferred from another. When I mix an album project, I use at least two or three different formats to print the mix. Most engineers and producers will have copies in another format. If they were mixing to Sony 1630 or Mitsubishi X-80, then they will also probably have printed a DAT tape at the same time.
If the project you are sending for transfer was released on CD, also send the released CD. Even if the particular tune to be transferred is not on the CD, valuable information can be ascertained by listening to material from the same project. For instance, if you are transferring TV mixes, listening to the CD can tell us whether emphasis was used, or the sample rate can be verified by comparing the pitch of the CD and the TV mix.
Even if the only other copy of the material is an analog tape, it could supply vital information that might otherwise go un-noticed.
If you are having analog tapes archived, send along other copies of the material. It is always best to make the transfer from the original master, but as stated earlier, important information can be obtained from EQ copies, or copies that were made to send to the cassette plant. It may also help to send along a vinyl record of the project if that is available. There have been cases where I have received an original analog multitrack tape only to find out that the strings and horns were recorded on a copy, not the original.. The song had never been released, so if I hadn't had both tapes to compare, no one would have ever known. I transferred the original master and the copy, and was able to use combine the first generation tracks with the first generation strings and horns to produce a better sounding product than was originally recorded.
The Final Analysis:
The only way to avoid transferring audio from one format to another is to never record anything. In the days of analog recording, nobody considered transferring to new brands of analog tape because of the generation loss in analog to analog transfers. Now that we are in the digital era, transfers can be made to new formats with absolutely no loss whatsoever.
We talked about all of the digital formats that have dissappeared, but remember, there are literally millions of CD players out there. Archival CD-R discs are playable on any CD player, it doesn't have to be some special professional machine. You are guaranteed of always being able to retrieve your material. The next time you will have to worry about protecting your investment will hopefully be 267 years from now.
I hope that this explanation will help you ascertain the condition of your tape library and that your tapes can be transferred to a more secure medium. Recordings of sounds and music are important to people all over the world, and it would be a shame if these priceless masters were lost because of inaction. If you have any further questions, please do not hesitate to contact Digital Atomics for assistance. Digital Atomics is striving to "Preserve the Future of Your Legacy".
Roger Nichols
President
Digital Atomics Corp