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What is a plugin? What are the basic types of microphones? How does a mixer work? What does a patchbay do? The basic idea behind any tape is the electromagnet that applies a magnetic flux to the oxide of the tape.
This electromagnet is tiny — perhaps the size of a flattened pea. The electromagnet consists of an iron core wrapped with wire, as shown in the figure. In a nutshell because if it is enclosed, the magnetic flux will be so low. Thus, no changes will happen to the magnetic field of the medium tape. The most significant difference between the magnetic field and the magnetic flux is that the magnetic field is the region around the magnet where the moving charge experiences a force , whereas the magnetic flux shows the quantity or strength of magnetic lines produced by the magnet.
Second : if it is enclosed, we will have a transformer core. Not a solenoid. Well, ideally no! So yes, it does! Just as in the electrical case, there is a magnetic field outside the iron core, but no electrons are there to join the army, so not much flux results.
The small flux that does go this way is called leakage flux. Leakage flux is important in transformers. Each of the individual magnetic particles on the storage medium has its own magnetic field.
This oxide is a ferromagnetic material, meaning that if you expose it to a magnetic field it is permanently magnetized by the field. That ability gives magnetic tape two of its most appealing features:. These two features are what make tapes and disks so popular -- they are instant and they are easily changed.
If you look inside a compact cassette, you will find that it is a fairly simple device. There are two spools and the long piece of tape, two rollers and two halves of a plastic outer shell with various holes and cutouts to hook the cassette into the drive.
In a minute cassette, the tape is feet meters long. The simplest tape recorders are very simple indeed, and everything from a Walkman to a high-end audiophile deck embodies that fundamental simplicity. The basic idea involves an electromagnet that applies a magnetic flux to the oxide on the tape.
The oxide permanently "remembers" the flux it sees. A tape recorder's record head is a very small, circular electromagnet with a small gap in it, like this:.
This electromagnet is tiny -- perhaps the size of a flattened pea. The electromagnet consists of an iron core wrapped with wire, as shown in the figure.
During recording, the audio signal is sent through the coil of wire to create a magnetic field in the core. At the gap, magnetic flux forms a fringe pattern to bridge the gap shown in red , and this flux is what magnetizes the oxide on the tape.
During playback, the motion of the tape pulls a varying magnetic field across the gap. This creates a varying magnetic field in the core and therefore a signal in the coil. This signal is amplified to drive the speakers. In a normal cassette player, there are actually two of these small electromagnets that together are about as wide as one half of the tape's width. The two heads record the two channels of a stereo program, like this:. At the top of this picture are the two sprockets that engage the spools inside the cassette.
These sprockets spin one of the spools to take up the tape during recording, playback, fast forward and reverse.
Below the two sprockets are two heads. The head on the left is a bulk erase head to wipe the tape clean of signals before recording. The head in the center is the record and playback head containing the two tiny electromagnets.
On the right are the capstan and the pinch roller , as seen below:. The capstan revolves at a very precise rate to pull the tape across the head at exactly the right speed. The standard speed is 1. The roller simply applies pressure so that the tape is tight against the capstan. Most higher-end tape decks have controls like those below for different tape formulations and bias.
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