Tape recorder

A tape recorder is an audio recorder for analog sound recording on tape material. The latter consists of a thin plastic carrier material which is coated with a magnetizable layer having iron oxide, iron oxide and / or Chromoxidkristallen. Analog tape recorders and related cassette recorders were displaced by the advance of digital technology in the entertainment and studio electronics almost entirely from the market.

History

After more theoretical work done by Oberlin Smith (1878/1888) and the first, not fully market- compatible devices made by Valdemar Poulsen appeared in the late 1920s, steel wire Magnettongeräte mainly was for dictation and steel tape devices for the broadcast application ( Curt silence, Semi J. Begun ). After Fritz Pfleumer had in 1928 proposed as a sound buffer -coated magnetizable steel powder tape, put the tape recorder before 1935, the AEG, which with a group from the IG Colors Industrie Aktiengesellschaft delivered cellulose Azetatband worked. Since 1939, it was coated with the ferromagnetic iron oxide ( γ ) -Fe2O3. The first cantilevered coiled on winding cores magnetophon was 6.5 mm wide; since about 1948 sat as a uniform international bandwidth by 6.3 mm. This first device was later called full track devices, because the whole width of the tape is used to record ( = track) in one direction. The belt speed is low 100 cm / s, then 77 cm / s ( Germany ) and 76.2 cm / s (international, equivalent to 30 in / sec ), later 38.1 cm / s; was followed by further halving of tape feed down to 2.38 cm / s Amateur and semi-professional equipment used almost exclusively 19 cm / s or, with a slight loss of quality, 9.5 cm / s; in professional studio (radio and recording studios ) mostly remained 38.1 cm / s standard. In professional specialized equipment such as flight recorders, which depend primarily on long term use, there are some still lower belt speeds.

Since the late 1940s there were first half-track equipment that worked basically with wound on reel tape. This is recorded in the first pass to somewhat less than half the width of the tape. Then, no later than the end of the tape, the coils are reversed ( turned ) and in another run, the second track is recorded in the opposite direction. Thus, the game time will be doubled for the same length of tape.

From the early 1950s resulted in an increasing number of manufacturers tape recorders for the home on the market, with more and more technological opportunities and increasing quality:

• Track positions: Home tape recorders were first made ​​in half-track technology. Their track position - in the first pass, the upper half of the bandwidth is recorded - was not until 1956, however standardized, so all the tapes recorded with devices from different manufacturers were not compatible until then. Quarter track devices it was not until the late 1950s. Add half-and quarter -track recording recorded tapes not compatible ( half-track tapes but playable with qualitative restrictions on quarter track devices) were. Chance also devices were ( the component that houses the necessary for erasing, recording and playback converter ) available for half and quarter track head with exchangeable straps. The change required only a few handles. Rare to find were half-track tape recorders with an additional playback head for quarter -track recordings.
• Stereo: Devices with dual-channel recording for spatial sound reproduction also came out at the end of the 1950s.
• Several belt speeds: First, the band velocity 19.05 cm / s standard for home tape recorders. Then, however, was the speed - in favor of the term and at the expense of sound quality - repeatedly halved: 9.5 cm / s, 4.76 cm / s to 2.38 cm / s In some appliances the higher price and quality classes, the belt speed could be switched.

However, due to the high prices, the devices remained unaffordable for many retail.

First 8-track device with a bandwidth of 1 inch ( 1 inch = 25.4 mm), in the development of up to 24 tracks on 2 inch wide band (50.8 mm ) - For professional use multi-track tape recorders were a little later developed. This makes it possible to receive or 24 individual sound sources simultaneously or sequentially; while a track is assigned at the original recording any sound source. This allows the mixing happen later and repeat until satisfaction. Rare 32 -track devices for 50.8 mm band were delivered. Up to 48 tracks on a half - inch tape (12.7 mm) only allowed the few years applied digital recording technology with professional digital magnetic tape recorders. Reel tape recorders are now rarely used, occasionally they are found even in the professional field, especially in recording studios; but even there they are almost completely replaced by digital methods.

In the 1960s reel tape devices have been through the transistor technology compact, lighter and cheaper, and home tape recorders experienced a boom in sales. " The drill on the heels of the spread of the tape in the 1960s sought to a climax " ( Germany radio ). According to estimates of the backlog amounted to tape recorders in Germany in late 1962 about 5 to 6 million units; the degree of saturation was 25 % of households. The tape was "one of the most important media of information and documentation, cultural and political factor of the first order ( as an opinion of the Federal Council on the occasion of rejection of a payment obligation for private tape recordings ). " Over 50 models were of nearly a dozen manufacturers in Germany, including West Berlin to price of DM 250, - to DM 2000, - offered; The main customer was the age group 15 to 25 years, followed by the 25 - to 35 -year-olds. The popularity and economic importance of the home tape recorder increased continuously. 1965 Grundig, Philips and Telefunken designated according to the tape devices sector as a rapidly expanding branch of their production.

In the early 1970s exceeded the coils home tape recorders peaked, and developed in the past decade and featured cassette decks with Compact Cassettes (Audio Cassette ) entered the market. They in turn are much smaller than reel tape devices to use more convenient and " foolproof " because of the housing of a protected tape, also has a variety of pre-recorded music cassettes purchase ( MusiCassette ) offered. The significantly narrower band material permitted initially only a reduced sound quality, although the compact cassette was designed from the outset for music playback. After occasional missions to dictation purposes here even smaller tile systems prevailed with sufficient word intelligibility. That changed quickly, especially as from 1970 CrO2 tape material ( cobalt- doped iron later ) was developed, with the hi-fi quality was also possible. Electronic noise reduction systems (Dolby, HighCom ( Telefunken ) ) increased the sound quality noticeably again. Also new heads were developed that had a very long life ( Glasferritkopf ). Sparked the cassette players outside of professional applications, the coil tape recorders slowly.

The introduction of recorders with radio part, radio recorders, led to widespread use especially in youth culture. In the 1970s and 1980s, relatively large units with two cassette decks ( for quick Dubbing to another tape ) and powerful stereo amplifiers were built. The worldwide spread of the Compact Cassette system culminated in the battery-operated type players, the Walkman. A principal weakness of the compact cassette was that the ribbon guide - and thus the correct reproduction of the upper registers - depended on the specific injection precision of the cartridge case. Further problems in the handling, eg frequent " jamming, " by unequal tape, poorly running tape material or subsequent loss of quality of the recordings by unintentional magnetization etc. showed the limits of technology. New technologies, especially the early 1980s, developed compact disc ( CD) that eventually led to the displacement. First, the CD was used as a supplement to the higher audio cassette - in radio recorders additional CD players were installed. Many radio recorder also had built-in microphones - in Asia, for example, karaoke recordings are very popular.

Today, tape or tape devices are used less and less. In their domain -burned and pre-recorded CDs and DVDs and computer disks penetrated (especially with MP3 music files).

Construction and Technology

The default is to the left, the supply reel to the supply, in the middle of the head support with the tape heads and the capstan and the take-up spool on the right. In professional fields, and open reel tables are used as a bobbin serve the AEG- coil core (known as Bobby ) and NAB - ring.

To record serve two heads. First the belt runs over a pulley at the erase head (LK), which has a relatively wide head gap and a high frequency far beyond audible frequency - is fed from the extinguisher - usually about 80 kHz. A quality reducing DC erase head or hard magnet is rather rare in tape recorders. The actual recording is performed with a speech head ( SK ) having a slightly wider than the head gap Hörkopf (HK) in order to allow a sufficient flux of the magnetizable material, and so that sufficient levels and signal to noise ratio. The recorded low frequency is modulated with the high frequency from the extinguisher to avoid hysteresis, so-called bias magnetization. Typically, the bias at the output of the receiving amplifier is admixed, and Tandberg Akai gave an extra head on the backside of the tape with respect to the recording head, the bias added (Crossfield technique). To play a Hörkopf, which should have a narrow head gap as possible to achieve the highest possible cutoff frequency is used. For cheaper devices, only one cluster head is used both as a receiver and as a talking head, which is then designed for a compromise between both requirements. The merging of listening and speaking head, it is not possible to control the current recording instantly. You can listen to the recording head at just magnetized to the tape recording by the following playback head is called tape monitoring. This is a more complex electronics requires the separate circuits for recording and playback provides, through internal recirculation of the playback signal into the receiving channel but also so-called " multi-play " or an echo effect such as enables in the " Royal de Luxe " by Uher. Combined head device using the same electronics, which must be switched in each case as a recording amplifier or a reproducing amplifier, with the corresponding equalizing characteristics, and RF traps for the recording head has to provide the bias and the quench oscillator without disturbing the receiving amplifier. It is obvious that a tape recorder with quench oscillator and recording amplifier, erase head and recording head can be consistently optimized for shooting ( with 7 micron gap width ), while a separate playback head (2 micron slit width ) with optimized playback amplifier provides the best playback quality. Compared to the universal head unit although a higher head - adjustment effort is required, the higher distortion poorer magnetization of the tape, the better frequency response and accurate phase position (reference in the recording head is back gap edge, the playback head gap center ) meet more ambitious hi-fi requirements.

The head gap is not, in practice, an air gap, but rather a non-magnetic metal film of defined thickness.

In the " Royal de Luxe " by Uher it was another head, which allowed the setting of slide presentations with hand- controlled single pulses or super-8 films after Einheitstonverfahren. This so-called Diakopf took advantage of a special section of the tape as a pulse track to record the Tonfrequenzimpulse. (see also head clock )

The actual tape drive does not take place via the band plate, as this would be due to the continual changes in the diameter of the tape winding lead to speed fluctuations. The constant belt speed is ensured by a perpendicular, precision-machined steel shaft in close proximity to the microphone head, which has a well-defined diameter and rotates at high constant speed. This wave is called capstan or capstan, it is often chemically roughened to hold the slip during tape transport low. To this, the tape is pressed by a spring-loaded rubber roller ( pressure roller ). The band dishes are only there to then unwind the strip material with low resistance and wind up with a slight train on the other side. At home devices this is usually done by mechanical slip clutches whose drive is derived via intermediate gears from the capstan motor. In (semi-) professional equipment (eg Revox ) of the drive is done with three engines, two of which are responsible for the torque of both the disc and the third for driving the capstan. If the motor shaft directly carries the winding plate and acts as a sound wave, and the respective motor is controlled electronically, the mechanical structure can be simplified, while increasing the reliability, durability, low maintenance and sound quality.

The band calming role for the first time near the recording head used by Telefunken tape dampens longitudinal vibrations which would degrade as frequency modulation components play with modulation noise, perceived as roughness. This task can take a ball bearing in the left deflection mandrel ( Revox ) or a role in the tape guide ( ASC), which provides between record and playback head gleichzeitigt for optimal wrapping of the head mirror. The next higher belt speed is less longitudinal vibrations, which is reflected alongside wider frequency response in increased clarity and transparency. For good reason, use high quality tape devices high speeds and half- track position for stereo. At quarter track you can hear the talk about opposite lane at 19cm/sec in the bass. Quarter track has three grass tracks, half track only, the resulting larger usable track width improves the signal to noise ratio and also the Dropoutsicherheit in the recording, where a good band - head contact is critical important than during playback. In practice, unfortunately, often played tapes are less for new admissions, deformed band edges and tape debris prevent the required head contact for the uniform magnetization.

The tape speed in the coil is now tape recorders 9.5 cm / s, or multiple double or Half of them (19, 38, 76 cm / sec, 4.75 cm / sec). The value of 4.75 cm / s, is also used in audio cassettes. VHS video cassettes of the system running in standard speed under PAL about half as fast ( 2.339 cm / s), the actual band-to- head speed is larger by a multiple.

Every band has its specific optimum speed emphasis. For this change of the frequency response includes a standardized time constant. Here are lifted when recording high frequencies ( pre-distortion or pre-emphasis ), which are lowered when playing through the equalization ( de-emphasis ) again. With this method, the tape noise is reduced, the frequency response correction characteristic behavior of the web materials and the headroom optimized for all frequencies in music are not identical maximum amplitudes, much less suitable for tape saturation.

Noise reduction systems such as Dolby -A in the professional field, DBX or Dolby -B on the home Hi-Fi systems can significantly improve the signal-to- noise ratio. They require not only a linear frequency response of the tape recorder between recording and playback usually also a standardization of the level, because their level-dependent operation is optimized at high levels after dynamic range and at low levels after noise reduction. With Dolby B performs a level - mismatch to frequency response errors, as is a loss in level due to storage and the onset time loss of brilliance.

Major manufacturers of tape recorders

• AEG
• Akai
• Ampex
• ASC
• Brown
• Dokorder
• Dual
• Ferrograph
• Grundig
• Körting
• Nagra
• Metz
• North Mende
• Otari
• Philips
• Pioneer
• Revox / Studer
• RFT (brand of broadcasting and telecommunications industry of the GDR )
• Saba
• Schaub- Lorenz
• Sony
• Stellavox
• Tandberg
• Teac / Tascam
• Technics
• Telefunken (see also Magnetophon )
• Tesla
• Uher
• Unitra (Polish units)