As the tape passes by, these pulses align the tiny magnetic particles into patterns, leaving a record of the sound.įinally, the tape moves across a dedicated playback head, which “reads” the magnetic information stored on the tape and converts it back into electrical signals that are sent to the machine’s outputs. Between the positive and negative poles of each magnet is a tiny gap where an electromagnetic field is created that fluctuates in response to the changing signal. Next comes the record or sync head, which is essentially a stack of magnets (one per track), each wound with a coil of wire. First the tape passes over the erase head, which (if the track is armed) scrambles anything stored on that track.
In an audiocassette player, the tape must move from the supply reel to the.
#Tapedeck magnetic feild series
Tape heads for stereo cassette tapes must record on two tracks simultaneously.Between the reels, the tape passes over a series of magnetic heads that convert audio signals into magnetic energy and back again. magnetic field, a vector field in the neighbourhood of a magnet, electric current, or changing electric field, in which magnetic forces are observable. A tape recording can be erased by using a rapidly changing magnetic field. Rather their magnetic domains are reoriented by the magnetic field from the tape head. The oxide particles themselves do not move during recording. The oxide particles are on the order of 0.5 micrometers in size and the polyester tape backing may be as thin as 0.5 mil (.01 mm). But chromium oxide and metal particles provide a better signal-to-noise ratio and a wider dynamic range. The magnetic field produced in a ring of ferromagnetic material fringes out to the tape. Iron oxide has been the most widely used oxide, leading to the common statement that we record on a "ribbon of rust". The basic tape head action involves an oscillating current in a coil. The recording medium for the tape recording process is typically made by embedding tiny magnetic oxide particles in a plastic binder on a polyester film tape. The head is about 7 mm from left to right in the image. The structure to the left of the head may be for erasing. This is the head structure in a Kenwood tape deck.
For stereo cassette tape heads, there are two such mechanisms to record and playback from parallel tracks on the tape. The magnetic field produced in a ring of ferromagnetic material fringes out to the tape material at the gap. The basic tape head action involves an oscillating current in a coil. Tape heads for stereo cassette tapes must record on two tracks simultaneously. Thus the same head can be used for recording and playback. If an already magnetized tape is passed beneath the head, it can induce a voltage in the coil. A coil of wire around the ring carries the current to produce a magnetic field proportional to the signal to be recorded. Tape heads are made from rings of ferromagnetic material with a gap where the tape contacts it so the magnetic field can fringe out to magnetize the emulsion on the tape. An electric current in a coil of wire produces a magnetic field similar to that of a bar magnet, and that field is much stronger if the coil has a ferromagnetic (iron-like) core.
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