The main elements
of a magnetic head are the coils and the gaps (two sets, each one corresponding
to a stereo channel). These gaps end up on the surface of the head, on which the
tape passes at a certain speed, and are separated by a space of very small size
filled with non-magnetic material that separates both poles; the dimensions of
the gap are expressed in microns and their definitive value depends on the type
of application of the head and the investment (time and money) that the
manufacturer has destined for its production.
The operation of a magnetic head
is as follows: the coil, when receiving the electrical variations of the audio
signal, produces a magnetic field in the gap, field that varies in intensity
and polarity according to the changes of that signal. This magnetic field flow
circulates through the oxide of the tape to cross the gap. The result is a
magnetic variation, printed on the moving tape, which corresponds to the
changes in the audio signal. If the gap is too small, the magnetic flux will
tend to circulate by the gap instead of the sensitive layer of the tape.
The
magnetic field in the gap is a magnetic representation of the audio electrical
signal circulating through the coil. When the tape passes before the head, its magnetic
particles (which up to that moment presented a random disposition) are affected
by constantly variable magnetic field of the gap.
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