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CASSETTE TAPE HEAD Audio tape is a magnetic storage material. The audio is stored on it as varyied levels of magnetic density. The 'head' in cassette tape player converts the fluctuations in the magnetic field (on the tape) into an electrical A.C. waveform. The output is at a VERY low voltage. A preamp equalizer is the first circuit after the head. If a sine wave sweep (from 20-20,000hertz) is accurately recorded onto a cassette tape (the magnetic density is equal throughout the sweep), the audio head would not be able to accurately reproduce the correct voltage level across the sweep of frequencies (especially at the lower frequencies). The equalizer circuit is employed to 'flatten' the response of the audio output and therefore produce a more accurate output. The same thing is true for magnetic cartridges for playback of vinyl LPs*. * An LP is a black vinyl disc with grooves cut/stamped into it (in case you've never seen one of these relics). :)

MULTICHANNEL PLAYBACK In a previous section, we said that an 'autoreverse' tape deck could play both sides of a tape without manually flipping the cassette. On a standard stereo cassette tape, there are 4 tracks of audio. Each 'side' of the tape has a left and a right channel. A typical stereo tape head has 4 individual magnetic pickups. Each pickup basically consists of a magnetically conductive material wrapped by a coil of wire. The wires of the coil are connected to terminals on the back of the head. The diagram below shows the parts of a typical audio head.

The tape guides keep the tape properly positioned over the head.The mounting tabs are obviously used for mounting the head. Sometimes the mounting system will include a spring under the head. When there is a spring under the head, the mounting screws will also be used to align the tape head azimuth. Many car tape transports are made of stamped steel parts which may have a significant amount of variation from one piece to another. The azimuth adjustment is required to make sure the head is properly aligned with the tracks on the tape.

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