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Record player - tape


Record player - tape
Progenitor recorder - telegrafon - was invented by Danish physicist Valdemar Poulsen. In 1898, Poulsen has created a device that uses the phenomenon of residual magnetization and converts sound waves into magnetic pulses, which are recorded on a thin steel wire. On telegrafona input connected audio source - microphone. The current supplied to the electromagnet has a special shape. Produced by an electromagnet magnetic field magnetizes the steel wire, which is moving at a certain speed past the magnet. In time transfer sound from a microphone removable current increased or decreased and, consequently, increases or decreases the magnetic field generated by the recording magnet.

To play the sound track wire passed by playing a magnet. During the movement of the magnetic field lines intersect the coil windings of the phonogram, in which as a result of the law of electromagnetic induction, an electric current corresponding to the recorded sounds to the wire. These weak electrical pulses are converted into sound waves in the phone. They listened to the amplifier without using headphones. The sound quality was very low, and telegrafon not widespread.

It took thirty years to a wonderful invention Poulsen gained recognition. This was facilitated primarily the emergence and development of vacuum tubes amplifier circuits based on them, as well as improvement of the recordings. Wire tended samorazmagnichivatsya quickly. To compensate for this unpleasant property, it had to increase the speed of its movement, which initially reached several meters per second. Even a small track required a huge number of wires. Although its thickness is not less than 0, 1 mm coil with a record took a lot of space and were very heavy. A thin wire is torn, confused, twist during movement. She tried to replace the steel tape. Breaks have stopped, but the volume and weight of the recordings has increased several times. To unwind reel to a tape required a powerful electric motor. Running gear gets very cumbersome. During this period, the magnetic recording gave unpromising results.

Commercial success came to the recorder only after the invention of new recordings. German inventor developed the technology Pfeymer applying a layer of iron powder on the paper tape: new recordings well magnetized and demagnetized, it can be cut and glue. Subsequently, the paper tape replaced plastic - cellulose acetate, more durable, flexible and non-flammable. On the tape sputtered ferromagnetic powder (iron oxides), pre-mixed with a binder (for example, nitrovarnish). For the first time this tape began producing in 1935 the German company AEG. Tapes revolutionized the magnetic recording. It was a light, compact, well-kept magnetization, which allowed dozens of times to reduce the rate of recordings. In such a film could write a much longer product than on the wire.

Taping occurred as well as the wire. From all this it is clear that the most important elements were tape recording and reproducing the electromagnets, which are called magnetic heads. Both heads were magnetic cores covered the coils. At the core there was a gap filled with foil made of special bronze. The current passed through the coil of the recording head, forms a magnetic field that passes through the magnetic core and going out of its working gap in the surrounding area. When the field was constantly, it is magnetized uniformly all passing through the tape. When passing through the head coil electric current arising from the impact sound at the microphone, a magnetic field in the gap of the head varied depending on the current microphone, that is in accordance with the strength of sound vibrations. Tape acquired with different magnetization, and turned into a soundtrack. Various portions thereof provides various magnetized as in strength and direction. The magnetic field lines of the individual portions confined in a space formed outer magnetic field. When playing a sound track of the magnetic tape at the same speed as in the recording, I move the playhead past and aroused in her winding electric current, which varies according to the strength of the magnetic field of the tape. The current is then caused in the winding and reinforced, fed to the speaker.

To reuse the same tape had erasing head, fed by a special tube generator of high frequency currents. The current produced by this generator is passed through a winding erase head. While the tape is passed through the field generated by this head, she repeatedly magnetization-reversal and as a result left her in the demagnetized state. After erasing the tape come to the recording head. Here, each element was subjected to a double tape to a magnetic field, which was formed on the one hand, the recording signal current, and the other - an additional bias current flowing into the recording head of a high-frequency generator. This additional high-frequency current power supply has been called bias. It is necessary to deal with the distortions that had on sensitive tape, the various parts of the tape - especially lamps and transformers. While working around them created a sufficiently strong magnetic field, which magnetizes the tape also. For a long time it is undesirable magnetization (manifested when listening in the form of noise, crackling and hum) a very reduced quality soundtracks. Only after they learned to mix the signal to the current high bias current, the magnetic quality of the phonogram has increased so much that was to compete with the mechanical sound recording - phonograph record.

On the tape there were two coils - the serving and receiving. To move the tape served as a mechanism consisting of a motor drive shaft, the pressure roller and other parts. Typically, the device had to tape to rewind the tape from reel to reel in both directions.

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