ANALOG TAPE: DO IT YOURSELF?
60 years ago or so, it was easy to spot a die-hard audiophile because he or she
owned a reel-to-reel tape recorder. I was one of them. I owned an early
production-model Roberts, which was considered to be one of the serious
audiophile decks of its day. Although the manufacturers tried to make home
recorders as simple as possible, the whole process had a rather steep learning
curve. It’s even steeper today.
Record collecting can be relatively simple, particularly if a person sticks to vinyl
LP’s (which, will make the selection of a record turntable a lot simpler).
However, one can purchase a single turntable which will play all speeds and sizes
Analog tape recorders are mostly format-specific. Tapes recorded on different
format recorders are generally not interchangeable.
In order to be able to play 98 percent of the ¼” tape formats that were used, I own
(and have to maintain) four tape decks. This brings up the maintenance issue:
Tape recorders are very complicated electro-mechanical pieces of equipment for
which very few (if any) parts are still available. This also means acquiring the
proper test equipment and learning how to use it. If you want to try this yourself at
the hobby level, the most difficult task will be finding an affordable, working reel-to-
reel tape recorder to get started with. There are some talented technicians that
specialize in restoring old professional tape decks for archival purposes. As you
might imagine, these refurbished tape decks cost professional prices. The
alternatives are consumer and ‘Prosumer’ reel-to-reel tape decks. Some have
been expertly refurbished and good used ones can still be found.
For those who are new to analog audio tape recording, here is a link to a student
primer provided by the University of California, Santa Cruz titled:
. Check out the
page in my glossaries section for some
simple definitions and descriptions. Also visit my
page. Some of the sites
there have volumes of information about playing and archiving audio tape. You will
need to learn how to identify the various formats, adjust parameters such as
and be able to get the best out of decaying tapes that have been
improperly stored for years. I’m not intentionally trying to discourage you from
becoming a collector of audio tapes, I’m simply telling it like it is and suggesting
that you do some extensive research before jumping into a hobby that can easily
turn into a money pit.
One of the most popular uses for home reel-to-reel recorders was to make song
tapes of favorite songs from records or off-air. I made a few myself way back
when. This is the vast majority of what you are going to come across at garage
sales and swap meets. Some are OK, some are poorly made. Of course, a lot of
family history was recorded on reel-to-reel tapes, and this is what you may find in
Grandma's attic. On the other hand, there were quite a few commercial recordings
made for reel-to-reel enthusiasts, and some still survive. Some are very collectible!
Acetate base tape
The vast majority of family history recordings on reel-to-reel tapes that I have
archived were made from the middle 1950’s through the 1960’s. This was the era
of acetate tapes that are now very brittle and delicate. This type of tape is prone to
breaking and leaving jagged ends that are difficult, if not impossible, to repair.
Acetate tape can be identified by holding the reel up to a bright light. If you can
see light through the reel, it’s most
likely acetate because the acetate
base is clear.
Fig. 1 is a 7” reel of acetate tape
being held up to a 40 watt light.
The light transmission properties are
Polyester tape, (Fig 2.) when held up to
light, is opaque.
(The light on the surface of the reel is the
The one caveat here is that if the acetate tape in question is suffering from a
deformity called ‘cupping,’ it may not pass light edgewise as well as shown in the
example. Cupping is when the edges of the tape curl up somewhat, making the
tape resistant to wrapping on a reel. The tape itself looks like the shape of a metal
Venetian blind. Cupping results from the tape losing moisture over time. If severe
enough, cupping can cause the oxide to fall off the backing. You will usually notice
the oxide flaking condition on the outer wraps of the reel. While making acetate
tape easier to identify because the clear base is now identifiable, flaking is non-
reversible. If any of the recording has separated from the base, it’s gone forever,
turned into a small pile of oxide flakes. I
f the Cupping condition is not severe, there
is a possible treatment that can be done called a “B-Wind” whereby the tape is
wound onto a take-up reel with the oxide out. The tape reel is stored for a period of
time to possibly reverse the condition.
Acetate tape that has become too brittle to be playable can sometimes be re-
hydrated. The short story is that acetate tape usually can be re-hydrated if left in a
moist environment. This can be as simple as placing some dampened (not wet)
cotton balls in the corners of the tape box with the tape for 24 hours or so, or as
complex as making up a system which suspends the tape over distilled water in a
closed environment and left for a period of time. The key is to
have the tape
come in contact with the source of the moisture. I have written a separate article
on this subject which goes into more detail:
Moisturizing Acetate Tape
. If you have
old tape you suspect is brittle acetate, consult a professional or do some research
before attempting anything. The information is out there.
Polyester base tape
Polyester base audio tape first appeared on the market in the early 1950’s, and, by
the late 1960’s, it had basically replaced acetate tape. Polyester base audio tape
was readily embraced by the professional audio community because the improved
oxide formulations allowed for increased dynamic range. Unfortunately, during the
mid 1970’s, many manufacturers changed their oxide formulation (mainly the
binder and lubrication chemistry), and things started to go bad from there. Some of
those newer tape formulations had severe oxide shedding problems.
As it turns out, that was an indication of things to come in later years.
A surprisingly large percentage of polyester tape that was made in the last 40
years or so, suffers from a condition known as binder hydrolysis. This is a
condition whereby the binder (used to adhere the oxide formulation to the
polyester base) has absorbed moisture over time, causing the oxide to become
soft and sticky and leave oxide deposits on all of the stationary tape recorder parts
(Guides, Heads, Tape Lifters, etc.). Quite often, the tape will chatter across the
tape heads as the result of a condition known as
Ampex Corporation, one of the manufacturers plagued by the reformulation
problems, came up with the solution of ‘baking’ audio tapes at 130 degrees
Fahrenheit for 12 to 24 hours, depending on the size of the reel and the thickness
of the tape. Much has been written about this process, and the research
continues. Baking is a temporary solution because after a week or so at room
temperature, the problem tapes will return to their sticky state. Experience has
shown that polyester tape can be baked more than once. The possibility of
adverse affects resulting from audio tape baking is still being debated.
I discuss the baking process in a separate
Identifying the track format
One of the simplest ways to
identify the track format of a
recorded tape is to view it with a
magnetic viewer. This is a gadget
that has extremely fine magnetic
particles suspended in a fluid.
When placed over a recorded
tape, the magnetic viewer shows
the actual magnetic recording and
reveals the track format….almost.
Here are two pictures of recorded
tapes revealing their format under
a magnetic viewer:
(Right) is a 2 track stereo
recording. However, it could be a
half-track mono (recorded both
directions), since the two formats
share almost the same track width
and placement (0.01” difference).
If the picture above is a half-track
mono, one channel will play
forward and one channel will will
play backwards, when played on a 2 track machine.
Quarter track can be recorded in both directions. If that is the case, you will see
four bands of magnetism. That would mean it could also be a four channel
recording which, shares the same quarter track widths and spacing. At least, by
viewing the tape with a magnetic viewer, you can tell which play head format to
use for continuing the investigation.
If the quarter track tape shows four bands of magnetism, you will have to play it
one direction and then turn it over and check the other direction on a quarter track
tape deck. If the tape plays correctly in both directions, it’s a quarter track recorded
in both directions. If one of the directions plays backwards, you’ve probably got a
four channel tape on your hands and will need a four channel tape deck to play it.
A quarter track tape recorded in both directions (most likely stereo), played on a 4
channel tape deck will play both forwards and backwards at the same time.
Likewise, a quarter track tape recorded in both directions and played on a 2 track
tape deck will play both forwards and backwards at the same time with one
channel being lower in level if your machine is calibrated correctly.
Audio tape thickness is basically determined by the material used as the base. The
actual measurement is of the overall thickness. The oxide and the back coating (if
used) are very thin. The measurement itself is in one-thousandths of an inch and is
expressed in mils. All acetate back tape is 1-½ mils thick.
All professional tape is 1-½ mils thick. Polyester backed tape comes in three
thickness; 1-½ mil (also expressed as 1.5 mil), 1 mil and ½ mil which, is often
expressed as .5 mil. The thinner tapes may give a better head wrap, but that’s
about it. The downside of using a thinner tape is that there is more of the
possibility of crosstalk between the layers. Particularly, if the tape does not have a
Lubricating audio tape
I will lubricate a tape suffering from binder hydrolysis or sticky shed syndrome first
because I consider baking to be a last resort. I have found that the method and
product that I use for lubricating polyester base audio tape to be about 90%
effective. If the oxide appears to be sticky or shedding during the lubricating
process, resists you in any way, stop and read my articles on baking or lubricating
audio tape to possibly determine if you should proceed. There are several
approaches, using a number of products and chemicals currently in use to
lubricate audio tapes. I use a lubricant specifically formulated for audio tape
. Check out their website. They make products for
records and tapes along with information on how to use them.
I often have to use more lubricant on problem tapes than recommended by LAST
Factory. As you may have guessed, I have a custom built setup that I use for this
process. However, you can simply wet a cotton
or any lint free cloth
the lubricant and apply it to the oxide while rewinding or forwarding the tape
. By slowly I mean roughly 5–15 inches per second. You can play the tape
as a convenient way to move it at a constant speed while applying the lubricant
however, I would recommend threading the tape directly from reel-to-reel. If you do
play the tape, I would recommend applying the lubricant on the incoming side of
the tape before it comes in contact with the heads and I would also recommend
covering the heads with Teflon
tape. Teflon tape is very slippery and will protect
the valuable oxide, plus it avoids unnecessary head wear. While applying the
lubricant, Use an eye dropper to keep the cloth
wet. The kit from Last Factory
usually comes with applicators so try them to see if they work better for you. Stop
as often as necessary to re-fold the cloth and wet it again. The lubricant does
evaporate quickly from the oxide however, I have not encountered any adverse
effects from the layers winding onto the take-up reel before the lubricant has
evaporated completely. While I don’t drench the tape, I do make sure that the
coverage is such that the oxide gets wet. Because I’m coming in direct contact
with the fluid, I wear rubber gloves or disposable food handling gloves for the
application process even though I have been personally assured by the
manufacturer that all of their products are safe to handle. I’ve used Last Factory’s
tape preservative on all types of polyester base audio tape and acetate base
magnetic film as well with good results. I do not recommend lubricating acetate
base audio tape although the manufacturer says it’s OK. Magnetic film (16MM,
35MM etc.) is different in that the acetate base is several times thicker than audio
tape and so is the oxide coating. LAST Factory claims that treating magnetic
media with their lubricant will increase shelf life. I have only
support this, but I can say that I’ve noticed no adverse effects on my own tapes
after about twenty years of storage. I have recently added an article dedicated to
lubricating audio tape
Baking Polyester Tape
First, I will only bake a tape as a last resort when no other restoration method is
applicable. I use a food dehydrator. It can be that simple. The dehydrator I use
regulates the temperature by manually adjusting the air flow through the unit. It’s a
simple dehydrator which has no temperature gauge. To make sure that things are
at the correct temperature, I use a very accurate digital thermometer with a long
probe that allows me to monitor the temperature at the tape reel.
I typically use a constant temperature of 118 - 120 degrees Fahrenheit (48 - 49
degrees Celsius) or less. You can be within 5 degrees or so and be fine. At 120
degrees, the baking time will be 8 to 12 hours for ¼” tape. If you want to be safe,
operate on the low side and bake the tape longer. I’ve baked tapes around 115
degrees Fahrenheit for 24- 48 hours and longer with great results. Avoid
temperatures exceeding 130 degrees Fahrenheit (54.5 degrees Celsius) because
you will risk damaging the tape.
I have also written an article dedicated to
baking audio tape
Know that not all brands or types of polyester audio tape will respond to the baking
process. Make absolutely sure of the type of tape you have. Research it well
before trying anything.
Whatever type or brand of oven you use, it has to be temperature stable within a
few degrees. Because the air temperature and humidity are ever changing, (time
of day, time of year), I run my dehydrator for several hours while monitoring the
temperature at the area where the tape is to be placed
I begin the process
of baking any tapes.
Any oven used for the purpose of baking magnetic tape should not be used for
anything else. It should go without saying that a food dehydrator should not be
used both for food and magnetic tape.
Always, always seek advice from a professional before trying anything for the first
Transferring Reel-to-Reel Audio Tapes
I’m not sure how to describe a process that takes years of experience. Getting the
best possible transfer is much more complicated than just threading up the tape
and pressing the Play button. I would start by doing lots of due diligence (a legal
term). Do the research and learn everything that you can. There are some articles
on this site that will help.
While there are several formats, the Compact Cassette is the most common.
The word ‘cassette’ is a French word meaning: “little box.” The technology was
originally designed for dictation machines and the format was monaural or ‘mono’
which could be recorded in both directions. Compact cassettes became a
consumer format in the early 1970’s and the format was stereo that could also be
recorded in both directions. The tape itself is poorly supported which, in most
machines, causes skewing that leads to azimuth and wow and flutter problems.
Many cassette machines run at slightly different speeds making for compatibility
problems. You will find that many audio cassettes have been recorded with peaks
well above the normal recording levels than the tape was designed for. When it
comes to transferring cassettes that were recorded in mono or stereo, the main
problem is azimuth. I prefer to use a dual capstan machine for the format. A dual
capstan machine tends to hold the tape steadier. Some Nakamichi cassette decks
have pad lifters which, can also be a bonus. Here is a guide to transferring
cassettes which, is a downloadable PDF file:
The only thing that I would add to the guide is to exercise all audio tapes by
shuttling the tape if it’s a reel-to-reel or fast-forwarding and rewinding if it is
cassette based, before transferring. Use the shuttle mode if your tape deck has
one for reel-to-reel tapes. Some tape decks make tape head or lifter contact in
shuttle mode which, is a bad thing.
Learn what a cassette in good condition sounds like while fast-forwarding and
rewinding and listen while exercising each one.
Storing Audio Tape
All of your audio tapes, records, and optical media should be stored vertically (on
edge). Store all of your magnetic audio recordings in a cool dry place that is away
from excessive heat or moisture. (So, how many times have you read that on the
label of a flour box?) Well, it’s true. Keep all of your magnetic media in an area
where the temperature and humidity are the most stable. Large fluctuations in
either will accelerate deterioration. Check with your local librarian or the Internet
for information on this subject. Archivists recommend an average temperature of
less than 50 degrees Fahrenheit (10 degrees Celsius) and 30 - 40% relative
humidity or less. Those ‘ideal’ conditions may be difficult to attain in the average
home, but maintaining room temperature at 30 - 40% relative humidity (or less) is
possible. This likely leaves out the basement and attic unless one or both have
been built to maintain a stable temperature and humidity year round. Storing your
magnetic media on the highest shelf in a centrally located closet will probably be
the most stable environment in the average home. I live in the desert mountains
on the West Coast of the US, where a closet shelf works well and the audio tapes
have faired well over the years.
Analog tape recording has seen a niche resurgence by artists who prefer the sonic
characteristics of analog tape. During the heyday of analog recording, there were
a dozen or more manufacturers of tape stock and as many manufacturers of
recorders. Today there are only a couple of manufacturers of analog tape left and
nobody, that I know of, is making new reel-to-reel recorders.
I would be remiss if I didn’t mention again that if you have some old family
recordings and you are the least bit unsure about them, please consult a
professional before doing anything. You may have only one chance to play them.
My advice is always free and their is a ‘Contact Me’ button at the top of all pages.
© Corey Bailey Audio Engineering
DO IT YOURSELF?
BAKING AUDIO TAPE
LUBRICATING AUDIO TAPE
A Little About Sound
Optimizing your PC
Packing Records for
People I have Known
Playing Records Wet
Playing a Wire Recording
Saving Your Family Video
Tubes vs Transistors
Your Digital Data is at Risk
What Type of Wire?
FIG. 3: 2 Track format
FIG. 4: 1/4 Track format
The picture to the Left,
(Fig 4) is that of a quarter-
track stereo format to
show the difference in