Tape recorder is a device for recording sound, pictures, and various other kinds of data on magnetic tape. It can also play back tape recordings. Tape recorders are widely used by the recording industry and in radio and television broadcasting. Millions of people enjoy listening to music or recorded books on tape recorders in their homes and automobiles or on portable tape recorders.
Tape recordings can be edited by cutting out the unwanted sections and then joining the ends of the tape. But tapes are less durable than compact discs (CD’s).
This article deals with audiotape recorders, which record only sound. For information on tape recorders that record visual images as well as sound, see Videotape recorder .
Audio recording tape is a thin plastic ribbon coated on one side with particles of a substance that can be easily magnetized, such as iron oxide or chromium dioxide. A tape recorder receives sounds in the form of electric signals, which it converts into a changing magnetic field. During recording, the field arranges the particles on the tape into magnetic patterns. When the tape is played back, the magnetic patterns generate electric signals that the recorder uses to reproduce the original sound. Tape recording can be accomplished by two different processes: analog recording and digital recording.
In analog recording, the patterns of the electric signals are analogous (similar) to those of the magnetic signals. Analog tape recordings store a signal in a form that looks like the wave form of the original sound. In a digital recording, the electric signals are converted to a digital (numeric) code for storage on the tape. This code represents the sound. Digital recording produces better sound quality with less background noise and distortion than analog recording does.
How tape recorders work
Most audiotape recorders operate in a similar way, whether they are analog or digital. Magnetic tape unrolls from a supply reel and is wound onto a take-up reel. Between the two reels, a soft rubber pinch roller presses the tape tightly against a metal rod called a capstan. During recording and playback, a motor turns the capstan. The turning capstan pulls tape from the supply reel. At the same time, the take-up reel pulls gently on the tape to wind it up.
Before the tape reaches the capstan, it passes the heads of the tape recorder. The heads are small electromagnets that erase, record, and play back. The speed at which the tape moves past the heads depends on the type of tape recorder. The speeds are measured in inches per second (ips). The most commonly used speeds are 17/8, 33/4, 71/2, and 15 ips (4.8, 9.5, 19, and 38 centimeters per second). The higher speeds produce recordings of the best quality, but recording at slower speeds increases the playing time of the tape.
Erasing and recording.
When an analog tape recording is made, the tape first comes into contact with the erase head. The erase head, which is automatically activated during recording, produces a strong magnetic field that removes any previous recording from the tape. The blank tape then moves past the recording head.
A microphone translates the sounds to be recorded on the tape into a varying electric current. An amplifier strengthens the current, which is then fed into the recording head. As the current flows through the head, it sets up a changing magnetic field around a small gap in the electromagnet of the head. When the analog tape passes the gap, the magnetic field arranges the magnetic particles on the tape into a pattern that represents the sound waves entering the microphone.
Unlike analog recorders, most digital recorders have no erase head. Instead of erasing the tape first, they use a process called overwriting to record new sound. Recording and playback heads may be either stationary or rotating. Stationary heads are like the heads on an analog tape recorder. In a rotating system, two heads are mounted opposite each other on a rotating cylinder called a drum. During recording and playback, the tape moves past the spinning drum.
A digital audiotape recorder converts the original electric signals to digital information in several steps. First, the signal is filtered to prevent interference from unwanted high frequencies. Next, each second of sound is broken up into thousands of segments called samples. Each sample corresponds to a specific numeric code, which is recorded on the tape in the form of a magnetic pattern.
Different kinds of tape recorders use different widths of magnetic tape. Most tape recorders can record more than one track (separate recording) on a tape. To produce stereophonic sound, a tape recorder must record at least two tracks at the same time, each track from a different channel of sound.
Playing back.
Before a tape recording can be played, it must be rewound on the supply reel. The tape is then sent through the recorder again. This time, the playback head is switched on, and neither the erase head nor the recording head is activated. As the tape passes the playback head, the magnetic patterns on the tape generate a weak electric current in the electromagnet. An amplifier strengthens the current before it reaches a speaker, which reproduces the recorded sound.
During playback, the pattern of the current generated by an analog tape corresponds to the pattern of the recorded sound waves. Playing a digital tape produces electric pulses that represent a numeric code. The recorder translates the code into a varying current, which an amplifier strengthens and sends to the speakers.
Kinds of tape recorders
There are two main kinds of audiotape recorders: open-reel and cassette.
Open-reel tape recorders
are used by recording studios and broadcasting stations. They produce better-quality sound than do cassette recorders. To use an open-reel recorder, the operator places a supply reel and a take-up reel on spindles on the outside of the recorder. The tape is threaded by hand past the heads of the recorder and through the capstan and pinch roller.
Recording studios usually record at 15 or 30 ips (38 or 76 centimeters per second). Many professional analog recorders use 2-inch (5-centimeter) tape, which carries 24 tracks. Professional digital recorders often use 1/2-inch (1.3-centimeter) tape, which carries up to 48 tracks. Such analog and digital recorders are called multitrack tape recorders.
Cassette tape recorders
are designed for use by consumers rather than recording industry professionals. They are easier to operate than open-reel recorders because the tape does not have to be threaded through them. A cassette recorder uses a small plastic case, called a cassette, which encloses a miniature supply reel and take-up reel. The cassette is snapped into the recorder. Many cassette recorders have electronic noise reduction systems, which reduce the faint hissing sound made by the tape.
Cassette tape measures only 0.15 inch (3.81 millimeters) wide. Analog cassette tape carries four tracks, two on each side. It operates at 17/8 ips (4.8 centimeters per second).
A cassette deck, also called a tape deck, is a tape recorder that usually operates as a component (part) of a stereophonic sound system. Deck features called synchronized start and dubbing allow recordings to be made from CD’s or cassette tapes. An auto reverse feature switches the direction of tape movement so that both sides of the tape can be recorded or played back without removing and reinserting the cassette.
DAT (_d_igital _a_udio_t_ape) cassettes produce far better sound quality than do analog cassettes. A DAT cassette is smaller than an analog cassette but has a longer playing time. It uses two tracks and is played on only one side. A DAT cassette operates at 0.321 ips (8.15 millimeters per second), using a rotating head.
History
In 1898, Valdemar Poulsen, a Danish engineer, invented the first machine for recording sound magnetically. He called his invention the telegraphone. It used an electromagnet to make a magnetic recording on steel wire. However, phonograph recordings were more popular at that time, and little use was made of magnetic recording for a number of years.
A small number of audio recorders began to be produced commercially in the early 1930’s. Initially, steel wire and steel ribbon were the only recording materials used. But they were awkward to handle and store and nearly impossible to edit. During World War II (1939-1945), German engineers perfected the magnetophon, the first recorder to use plastic magnetic tape.
By 1950, tape recorders were being widely used in the radio and recording industries. Manufacturers began to produce stereo tape recorders for use in the home in the mid-1950’s. Cartridge tape systems were introduced in 1958. Such systems, which are often called 8-track, used an endless loop of tape in a cartridge to play four stereo music programs. Eight-track systems were especially popular for use in automobiles.
In the mid-1960’s, cassettes revolutionized the tape recorder market. They gained even greater popularity when noise reduction was added, and they began to compete with phonograph records.
Manufacturers introduced digital recording systems in the 1970’s. The market for prerecorded music became even more competitive in 1983 with the introduction of audio compact discs. CD’s gradually became more popular than audiotapes. Digital audiotape recorders became available in the 1990’s, but they had little success with consumers. In the late 1990’s, digital music recordings, which can be played on computers and digital music players, became available over the Internet. Since that time, cassette tapes have declined further in popularity.
