Cassette demagnetizer
Encyclopedia
A cassette demagnetizer is a device that removes the magnetic
field that is built up from the use of audio cassettes in a cassette deck
.
Over time, the passage of magnetically charged cassette tape over the metallic parts of the tape deck will impart a magnetic polarity that can impair the ability of subsequent tapes to record accurately. Cassette demagnetizers (sometimes known as degaussers
) were developed to remove this polarity.
Cassette demagnetizers of the "cassette" type physically resemble a cassette tape shell but contain circuitry
to demagnetize the tape head
s of the tape deck. Another type of demagnetizer, the "wand" type can demagnetize anything that it is brought into contact with, including the tape heads and capstans. Nakamichi
manufactured a "wand" type demagnetizer in the 1980s. This design had the advantage that it could be used to demagnetize other metal parts of the tape path (not just the actual record/playback heads) however it required careful use (to avoid increasing the magnetization of the heads) and if used too close to actual cassette tapes could inadvertently act as a "bulk eraser".
Demagnetizers contain electronic circuitry and require a power source—either a battery
or a power cord.
A third design consisted of a cassette shell with a head cleaning tape wound on the spools and a disc shaped magnet mounted above the head cleaner tape such that when the play button was activated the head cleaner physically cleaned the head surface and simultaneously made the magnet rotate, creating the alternating magnetic field required for demagnetizing.
Some cassette deck manufacturers even produced decks with a self demagnetise button. These worked by feeding the record head with a strong high frequency signal which was gradually reduced in amplitude to zero over a few seconds.
Magnetism
Magnetism is a property of materials that respond at an atomic or subatomic level to an applied magnetic field. Ferromagnetism is the strongest and most familiar type of magnetism. It is responsible for the behavior of permanent magnets, which produce their own persistent magnetic fields, as well...
field that is built up from the use of audio cassettes in a cassette deck
Cassette deck
A cassette deck is a type of tape recorder for playing or recording audio compact cassettes. A deck was formerly distinguished from a recorder as being part of a stereo component system, while a recorder had a self-contained power amplifier...
.
Degaussing
Degaussing is the process of decreasing or eliminating an unwanted magnetic field. It is named after Carl Friedrich Gauss, an early researcher in the field of magnetism...
) were developed to remove this polarity.
Cassette demagnetizers of the "cassette" type physically resemble a cassette tape shell but contain circuitry
Electronics
Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...
to demagnetize the tape head
Tape head
A tape head is a type of transducer used in tape recorders to convert electrical signals to magnetic fluctuations and vice versa.-Principles of operation:...
s of the tape deck. Another type of demagnetizer, the "wand" type can demagnetize anything that it is brought into contact with, including the tape heads and capstans. Nakamichi
Nakamichi
is an historic Japanese high end audio company most famous for its innovative and very high quality audio cassette decks.In 1972, Nakamichi launched its first Nakamichi-brand products, home audio gear that included the world's first three-head cassette deck...
manufactured a "wand" type demagnetizer in the 1980s. This design had the advantage that it could be used to demagnetize other metal parts of the tape path (not just the actual record/playback heads) however it required careful use (to avoid increasing the magnetization of the heads) and if used too close to actual cassette tapes could inadvertently act as a "bulk eraser".
Demagnetizers contain electronic circuitry and require a power source—either a battery
Battery (electricity)
An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 1800 by Alessandro Volta and especially since the technically improved Daniell cell in 1836, batteries have become a common power...
or a power cord.
A third design consisted of a cassette shell with a head cleaning tape wound on the spools and a disc shaped magnet mounted above the head cleaner tape such that when the play button was activated the head cleaner physically cleaned the head surface and simultaneously made the magnet rotate, creating the alternating magnetic field required for demagnetizing.
Some cassette deck manufacturers even produced decks with a self demagnetise button. These worked by feeding the record head with a strong high frequency signal which was gradually reduced in amplitude to zero over a few seconds.