from Wikipedia, the free encyclopedia
Tape on reel
Tape reels on a Telefunken Magnetophon 3000hifi tape recorder (1973)

A tape ( magnetic tape ) is a steel tape or a paper or plastic tape that is coated with magnetizable substances (e.g. iron (III) oxide , chromium dioxide or iron powder).

It was used in audio recorders ( tape recorders , answering machines , dictation machines , voice recorders ) as a magnetic storage medium for audio signals (speech, music, noises).

Similar media and formats are also used for video recording , as mass storage for digital information and as magnetic stripes in money and loyalty cards . See also magnetic tape .

For magnetic sound recording on film, see Magnetic Sound Process .

The term was also used in colloquial language as a short form for reel tape recorders.


Grundig portable tape recorder from the early 1960s

Steel wire was initially used as the sound carrier for magnetic sound recording. The Danish telegraph engineer Valdemar Poulsen invented the first device of this kind, and thus at the same time the basic principle of magnetic sound recording, in 1899 and called it the telegraphon . It worked in the original design with a piano string wound on a roller, was used to store telephone calls and caused a sensation at the 1900 World Exhibition in Paris. Early flight recorders also worked with wire, see also wire sounder .

The original tape was a steel tape on reels that was developed by Poulsen as an improvement to his telegraphone before the First World War . A similar sound carrier could already be played back on the Marconi steel tape machine via a special playback head (HK audio head).

Around 1928 , the German-Austrian Fritz Pfleumer invented the paper tape in Dresden. In 1935/36, the Badische Anilin- und Soda-Fabrik (BASF) in Ludwigshafen developed the first plastic tape, the L-type tape.

The Allgemeine Elektricitäts-Gesellschaft (AEG) presented the world's first tape recorder Magnetophon K 1 to the public at the 12th Great German Radio Exhibition in Berlin in 1935 .

In later tape recorders for radio and studio use, the tape was wound on open plates or on reels (reel tape recorders). Cassette tape recorders were later developed for home users. The most widespread was this the compact cassette system from Philips .

Smaller cassettes were mainly used for dictation machines and answering machines .

The term “tape” is often used synonymously with “reel tape” - in contrast to the “compact cassette”. Due to the increasing spread of the compact cassette as a recorded music cassette, the reel tape lost more and more importance in the home from the late 1970s, because the handling of the compact cassette was much easier: You no longer had to laboriously thread the tape, only the one Insert the cassette into the player.

Magnetic recording was later replaced in answering machines and dictation machines by digital storage on microchips. From the end of the 1990s, with the spread of the CD-R, the compact cassette was in turn replaced by the compact disc (CD) as a digital sound carrier. Another digital sound carrier was the minidisc . Meanwhile, MP3 players can use internal data compression to save longer, high quality recordings without special sound carriers.

But even today, tape machines can still be found in professional use, for example in music studios and on film sets. Tape machines are also still in use for the composition and interpretation of works of electronic music .

In parlance, the term “off the tape” is used for sound recordings that have been stored digitally on completely different media, for example with pre-prepared accompanying music by solo entertainers or exotic birdsong that can be heard in garden centers.

Band width and reel size

Tape running of a tape recorder
Self-supporting tape roll on a Bobby (AEG winding core)

In the Pfleumer experiments, the width of the tape was initially 16 mm (16 mm film reels were used), later in the experiment approx. 10 mm, then in the AEG before the Second World War 6.5 mm. After the German AEG devices were shipped to the USA, the 6.5 mm standard was changed to 1/4 inch (6.35 mm). Furthermore, the magnetisable side (layer side) of the tape was moved from the outside to the inside, this is referred to as the "international layer position". In German broadcasting, the layer layer on the outside (“German layer layer”) and only with self-supporting coil windings on a “Bobby” (AEG winding core) were often used. In the case of the compact cassette , the magnetic layer is again arranged on the outside for technical reasons (position of the read / write heads).

Since the end of the Second World War, the tape width has been 1/4 "= 6.35 mm or a multiple thereof - up to 2-inch tapes or only 0.15" (3.81 mm) for the compact cassette . The magnetic tape with a length of well over 1000 meters is wound on reels.

The diameter of the reels for the magnetic tapes ranges from 6 cm over 8, 10, 11, 13, 15, 18 and 22 to 26.5 cm, in old radio studios and in the USA even up to 16 "(about 41 cm). The sound is recorded on one or more tracks at the same time, there are 48-track digital devices and analog devices with up to 64 tracks.

Belt speed

The feed speed (tape speed) during operation influences the recording quality. At lower speeds, the frequency response changes, which is why tape recorders have an individual pre-distortion or equalization for each tape speed. The original belt speed was 77 cm / s. With a tape length of 1000 meters, this results in a recording time of almost 22 minutes. The value of 77 cm / s chosen by the AEG remained the standard speed in broadcasting for many years. When AEG magnetophones came to the USA after the end of the war, their first own models were largely based on the AEG devices. The conversion from 50 Hz to 60 Hz alternating current network (different motor speed) and from the metric dimensions of the AEG to the inch dimensions customary in the USA resulted in a slightly lower belt speed of 76.2 cm / s (equal to 30 inches) per second). By improving the tape material and electronics, the speeds could be reduced, whereby these have been halved. 76 cm / s are only used for professional, very high-quality recordings (master tapes in recording studios). When it came to broadcasting, they were committed to 38 cm / s and 19 cm / s. In home coil devices, 9.5 cm / s is very common. This speed is sufficient for recording radio broadcasts and interviews. The tapes have a playing time of one to two hours. For pure voice recordings, such devices usually also offer 4.76 cm / s. (By halving the values ​​that have already been rounded, 4.75 cm / s is often given.) For higher quality recordings, use 19 cm / s. In compact cassettes are generally 4.76 cm / s. Further speeds are 2.38 cm / s (for aircraft radio and session recordings as well as documentation purposes , dictation machines ), 1.2 cm / s for microcassettes for voice recordings.

In the English-speaking world, the belt speed is often given in inches per second (ips, "inches per second"). 1 ips is 2.54 cm per second, so, for example, a typical home coil machine will run at 3.75 ips.

When rewinding without operating the tape head, the pressure roller is not pressed against the capstan so that the tape can run freely from one reel to the other. Significantly higher speeds are achieved here.

For operation with the tape head as well as for rewinding, the tape must detach itself from the supply reel without any problems and, above all, accumulate cleanly on the take-up reel without, for example, corrugations occurring (if the take-up reel is pulled too high). In the case of professional tape material, a special back coating of the tapes (rear surface matting) helps . As a result, the tape reels sit securely on the reel carrier (bobby) in a self-supporting manner (without a reel). In the case of radio tapes, this is kept in a color (e.g. white) on which cutting marks can be clearly seen. In the case of the less frequently used endless cassettes, on the other hand, a lubricious coating ( graphitization ) is used. According to Bernard Cousino's method, there is only a single reel from which it is unwound at the same time - from the winding center - and rewound outside; therefore the tape layers must be displaceable relative to one another. This process was used by the 8-track cassette and its predecessor on the market, the Fidelipac / NAB cartridge.

Coloring of leader tapes

Repair and marking set for magnetic tapes from ORWO Wolfen

For professional use, the speeds and recording modes are identified by an internationally standardized color scheme for the leader tapes. In recording studios, for example, 7.5 inches or 19 cm / s for stereo recordings without time code are marked with blue and white leader tape. Only blue is used for mono recordings, but only for voice recordings on radio. Stereo recordings at 15 inches or 38 cm / s are marked with red and white and, when using time code, with red, white and black leader tape (broadcast standard). There are also special colors, if a noise reduction such as B. Telcom c4 or Dolby A was used for the recording, transparent tapes for the photoelectric switch off and yellow tapes as optical separators (for example between the interview sequences on the radio). Inch is the international unit of measurement here. Tapes for home use have a green (“beginning”) on one end and a red leader on the other. A switching tape made of electrically conductive material can be inserted between the leader tape and the actual tape, which triggers a transport stop on appropriately equipped devices.

The leader tape on the belt ends of compact cassette is in the winding core frictionally anchored by a radially pressed-in prismatic clamping piece. The clamping piece holds axially non-positively and radially positively and can thus be pulled out axially. The pretensioning strap has the following functions: On the one hand, it elastically cushions the end stop during fast forward or reverse travel; this is all the more important the thinner the tape used in the cassette. In addition, when handling the cassette, the user can see when the tape is at the very beginning or end. Occasionally, cassettes were advertised that the leader tape used should clean the tape head.


The magnetizability of ferromagnetic substances depends on their previous state ( hysteresis ). Therefore, the tape is first erased (i.e. demagnetized) before recording. In order to magnetize the particles in the layer, the field strength must exceed a certain threshold ( coercive field strength ). For this is through the pick-up head (voice head SK) next to the audio signal (voice stream) , a high frequency alternating current - the so-called bias (English. Bias ) - sent. The wavelength of the bias frequency (approx. 70 kHz) is small compared to the size of the magnetic particles of the tape or the width of the air gap of the recording head. The premagnetization ensures that the hysteresis curve of the layer particles in front of the gap is traversed. When the particles pass over the edge of the gap, the field strength decreases rapidly so that the speech current (which is quasi-stationary from the perspective of the layer particles) determines the final magnetization of each particle in the layer.

The erase head as inductance is part of the high-frequency oscillator that is also used for the premagnetization.

With radio recorders, when recording a radio broadcast in the medium wave range, an annoying whistling can occur if harmonics of the frequency of the extinguishing generator are close to the frequency of the received transmitter or the receiver oscillator . To avoid this, such devices have a button, often referred to as FU (frequency switching ) or Beat Cut , which slightly changes the delete frequency. The same problem occurs with the 19 kHz subcarrier ( pilot tone ) of the VHF stereo broadcast. This is lowered both in the VHF part of the radio and on the input side in the tape recorder so that any interference remains below the hearing threshold. The same applies to the 19 kHz pilot tone from which the subcarrier is regenerated in the receiver.

Alternatively, the deletion and premagnetization can also be carried out with constant fields . Except for the price, however, there are only disadvantages. In particular, tapes magnetized in this way with a constant field can more easily magnetize the components of other (also higher-quality) cassette or tape recorders during playback, which then erase recorded recordings. (Deleting means that the quality of the recordings deteriorates. In particular, there is a loss of height and a reduced signal- to- noise ratio .) In the past, this technology was only found in applications such as answering machines or dictation machines. Although the costs of a high-frequency pre-magnetization and erasure device in series production are very low today, DC field technology is on the advance again, for example with portable cassette devices and device combinations ( radio recorders ) - easily recognizable by a permanent magnet erase head, which is used during playback folds away or remains in a rest position.

At the end of the magnetic tape era, dynamic bias was developed. This improved the height control and thus the height dynamics at small wavelengths, i.e. low belt speeds. Compact cassette machines benefited from this, as did professional tape machines such as B. in the production of music cassettes, see Dolby-HX or the much better Dolby HX PRO developed by Bang & Olufsen .

Fresh tape and extinguishing tape

A fresh band, also known as a “virginal” band in jargon, is a brand-new band that has never been recorded in radio and recording studio technology .

An erasure tape is a tape that has already been recorded on that is no longer needed and can therefore be erased and then re-recorded on.

For recordings that will only be used in the near future, the more economical use of erasure tape instead of fresh tape does not pose a qualitative problem in practice. However, erasing tape is not suitable for permanent archiving for the following two reasons:

  • It is not possible to completely erase a magnetization once it has been applied. Over time, the initially deleted recording becomes quietly audible again under the current one.
  • Adhesive points in the tape can tear when the adhesive ages when the tape is played again.


For archiving purposes, tapes are kept in special air-conditioned rooms. They were initially (and still are) sensitive to temperature changes and humidity. With the further development of acetyl cellulose via PVC to polyester carrier material, this problem has almost been solved. A reduction in the quality of the recordings can result from unintentional magnetization such as magnetized playback heads or storage near insufficiently shielded speakers, etc. The copying effect can also occur.

Length and running time of common tapes

In addition to the tape length or the reel size, the strength ("thickness") of the audio tape is a decisive factor that affects the capacity of the reels. Different types of tape were available on the market, depending on the thickness of the tape:

Normal band
Tape thickness 50  µm . This type is used in the studio. The strength enables high mechanical strength and convenient cutting and gluing.
Long play tape
Tape thickness 35 µm. This achieves a reel capacity that is about a factor of 1.5 greater than that of normal tape. This type of tape is used especially in the hobby area.
Double play tape
Tape thickness 25 µm. This enables the reel capacity to be doubled compared to normal tape.
Triple play tape
Tape thickness 18 µm. It offers almost three times the reel capacity of normal tape, but must be handled very carefully as it stretches, kinks or tears easily.

Double and triple play tapes have traditionally been sold on smaller reels and, particularly when they were first introduced, were primarily intended for use on portable tape recorders. In addition, there were also products on the market with values ​​between long and double-play tape. Of the few remaining manufacturers of tape material, only normal and long-play tapes are made today.

Tape lengths with different reel sizes and types of tape

Coil Normal band Long play tape Double play tape Triple play tape
13 cm 180 m 270 m 360 m 540 m
15 cm 240 m 360 m 480 m 720 m
18 cm 360 m 540 m 720 m 1080 m
26.5 cm 720 m 1080 m 1440 m 2160 m

It should be noted that not every type of tape was available on every reel type. Usually, only normal and long-play tapes were offered on 26.5 cm reels.

Running times with different belt lengths and belt speeds

Tape length 4.76 cm / s 9.53 cm / s 19.05 cm / s 38.1 cm / s
180 m 63 min 31 min 16 min 8 min
240 m 84 min 42 min 21 min 10 min
270 m 95 min 47 min 24 min 12 min
360 m 126 min 63 min 31 min 16 min
480 m 168 min 84 min 42 min 21 min
540 m 189 min 94 min 47 min 24 min
720 m 252 min 126 min 63 min 31 min
1080 m 378 min 189 min 94 min 47 min
1440 m 504 min 252 min 126 min 63 min
2160 m 756 min 378 min 189 min 94 min

Major manufacturers of tape material

Web links

Commons : Magnetic Audio Tape  - collection of images, videos and audio files
Wiktionary: tape  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. Barry Kernfeld: Pop song piracy. Disobedient music distribution since 1929 . University of Chicago Press, Chicago / London 2011, ISBN 978-0-226-43184-0 , pp. 151 ( books.google.de ).
  2. Magnetic sound recording tapes . April 2, 1963 ( google.com [accessed May 2, 2018]).
  3. Maxell UD18 triple play tape 2,200 m. Tape machine forum, accessed on November 4, 2017 .
  4. Details DPR26. Christoph's tape pages, accessed on November 4, 2017 .
  5. a b tape lengths. STUDER and ReVox Infoportal, accessed on January 24, 2017 .