charismatic recordingis a moxie engineering science of the electronic age . It is a profound direction for for good storing info .
In this clause , we will appear at magnetized transcription . We ’ll focus on cassette magnetic tape and tape recorders , but the same technology applies to any form of magnetic transcription . You will read that the reason why magnetised recording is so pop is because it an easygoing and inexpensive engineering with full intermediate - term ( 10 to 20 years ) depot characteristics .
The Tape
There are two parts to any audio charismatic recording organization : the fipple pipe itself ( which also acts as the playback gimmick ) and the tapeline it uses as the reposition mass medium .
The taping itself is really very simple . It consists of a slender fictile stand material , and bond to this base is a coating offerric oxidepowder . The oxide is normally shuffle with a binder to attach it to the plastic , and it also let in some variety of ironic lubricant to avoid wear out the recorder .
branding iron oxide ( FeO ) is the ruby rust we usually see . Ferric oxide ( Fe2O3 ) is another oxide of iron . Maghemite or gamma ferric oxide are common name for the substance .
This oxide is aferromagneticmaterial , stand for that if you disclose it to a magnetised discipline it is for good magnetized by the field . That power yield magnetic tape two of its most likable features :
These two feature article are what make tape and disks so popular – they are insistent and they are easily modify .
Audio magnetic tape have gone through several format change over the years .
If you look inside a compact cassette , you will find that it is a fairly simple gimmick . There are two bobbin and the prospicient piece of tape measure , two hair curler and two halves of a formative outer shell with various holes and cutouts to hook the cassette into the drive . There is also a small feel inking pad that act as a backstop for the record / playback head in the tape recording player . In a 90 - moment cassette , the tape is443 feet(135 meters ) long .
The Tape Recorder
The simplest tape record-keeper are very simple indeed , and everything from a Walkman to a high - end audiophile deck embodies that fundamental simplicity .
The canonic idea affect an electromagnet that applies a magnetic magnetic field to the oxide on the tape . The oxide for good " remembers " the flux it sees . A tapeline recorder ’s record head is a very little , circular electromagnet with a modest gap in it , like this :
This electromagnet is tiny – perhaps the size of a flattened pea plant . The electromagnet consists of an smoothing iron heart wrapped with wire , as demo in the soma . During transcription , the audio signaling is mail through the spiral of telegram to make amagnetic fieldin the core group . At the gap , magnetized flux density forms afringe patternto bridge the gap ( shown in red ) , and this flux is what magnetize the oxide on the tape . During playback , the motion of the tape pulls a varying magnetic field across the gap . This make a varying magnetised field in the core group and therefore a signaling in the coil . This signal is amplified to drive thespeakers .
In a normal cassette role player , there are actually two of these low electromagnet that together are about as wide as one one-half of the tape ’s breadth . The two fountainhead memorialize the two channel of a stereoscopic picture programme , like this :
When you turn the taping over , you line up the other half of the magnetic tape with the two electromagnet .
When you look inside a tape recorder , you generally see something like this :
At the top of this moving-picture show are the two sprocket wheel that engage the spools inside the cassette . These sprocket spin one of the bobbin to take up the tape measure during recording , playback , fast forward and reverse . Below the two sprockets are two header . The head on the left hand is a bulk erase head to wipe the tape uninfected of sign before register . The head in the nitty-gritty is the record and playback school principal contain the two flyspeck electromagnets . On the right are thecapstanand thepinch roller , as envision below :
The capstan revolve at a very precise rate to pull the magnetic tape across the head at precisely the right upper . The standard hurrying is1.875 inches per second(4.76 cm per secondly ) . Therollersimply apply pressure so that the magnetic tape is tight against the capstan .
Tape Types and Bias
Most higher - end taping decks have ascendance like those below for different magnetic tape conceptualisation andbias .
Most higher - quality tapes state you their formulation by stating atype . There are four type of tape in plebeian utilization today :
level-headed calibre improves as you go from one case to the next , with metallic element tape receive the best levelheaded quality . A normal tapeline deck can not enter onto a alloy taping – the deck must have a place setting for metallic element tape so as to record onto them . Any taping actor can play a metallic element taping , however .
The controls on the tape deck have you match the recording bias and signal strength to the type of tape you are using so that you get the best speech sound potential .
Biasis a particular signal that is hold during recording . The first magnetic tape recording equipment simply use the raw audio signal to the electromagnet in the head . This works , but produce a lot of distortion on depressed - frequency sounds . A diagonal signal is a 100 - kilohertz sign that is added to the audio signal . The prejudice moves the signal being recorded up into the " analog portion " of the mag tape ’s magnetization curve . This movement means that the taping reproduces the sound memorialise on it more faithfully . Several of the links on the next page go into this topic in item , and also address Dolby noise - reduction systems .
For more information on tape recorder , cassettes , magnetic recording and related topics , hold out the links on the next page .
