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WPI Technical Theatre Handbook: Analog Tape
 
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Analog Tape

Most everyone is familiar with standard cassette tapes such as those used in consumer hi-fi gear. Analog tape works by magnetically encoding a representation of an audio signal on a long strip of metallized plastic. This strip of plastic moves past what is known as a head inside of the tape deck. Heads are responsible for converting the magnetic energy into electricity for playback, and vice-versa for recording. Other components inside of the deck help to keep the tape moving past the heads at precisely the correct speed. It should be noted that practically every component in a tape deck physically touches the tape, thus causing wear and tear on the tape itself.

While it can be argued that cassette tapes reproduce sound accurately, they are plagued by several other problems that reduce audio quality. Tape suffers from hiss (high-pitched sound that sounds like steam spraying from a pipe), dropouts (periodic loss in audio level), and wow and flutter (periodic changes in pitch due to the mechanics of the tape deck or the stretching of the tape itself). Expensive tape decks get around many of these problems with special electronics and high quality mechanisms.

Tape is not an especially robust medium. Inexpensive consumer-grade cassette tapes start to lose sound quality after they have been played even a few times. The most expensive cassettes last a few hundred plays before noticable degradation occurs, providing the deck they are played in is in proper working order. These are problems that significantly affect a theatrical performance, where shows are often run nightly for weeks on end. This makes tape an undesirable medium for the playback of sound effects or music for a production.

In addition to the lack of robustness of tape, it is not a medium that affords easy cueing. Accurate cueing (positioning the tape so that playback starts at the desired point) is something of an art, and is yet another unreliable aspect of cassette tapes. This makes tape difficult to use to play back sound effects accurately and on cue.

This does not, however, mean that tape is completely useless in a theatre setting. Multi-track tape decks are available that allow sound to be recorded in layers. This allows a convenient way to create complex sound effects when a computer is not available. Portable cassette decks with recording capability exist, thus they become prime candidates when recording sound effects at a remote location. Also, when working on a production that has music being composed for it, it may recorded ahead of time and presented to the audio engineer on a cassette. Cassettes tend to be the lowest common denominator as a medium that people can record and play back at their convenience. This offers some advantages, but they must be weighed carefully against the disadvantages of tape.

It should be noted that a lot of professional theatres still use analog tape in reel-to-reel format. Reel-to-reel allows reasonably easy cueing, and is a lot more robust than standard consumer cassette tapes.


next up previous contents index
Next: Digital Audio Tape (DAT) Up: Input Previous: Directionality   Contents   Index
Steve Richardson 2000-07-06

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