Stereo-Pak
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| Media type | magnetic tape |
|---|---|
| Encoding | analog signal |
| Read mechanism | tape head |
| Write mechanism | magnetic recording head |
| Developed by | Earl Muntz |
| Usage | Car audio playback |
The Muntz Stereo-Pak, commonly known as the 4-track cartridge, is a magnetic tape sound recording cartridge technology. The in-car tape player that played the Stereo-Pak cartridges was called the Autostereo, but it was generally marketed under the common Stereo-Pak trade name.
The Stereo-Pak cartridge was inspired by the Fidelipac 3-track tape cartridge system invented by George Eash in 1954 and used by radio broadcasters for commercials and jingles beginning in 1959. The Stereo-Pak was adapted from the basic Fidelipac cartridge design by Earl "Madman" Muntz in 1963 with Muntz partnering with Eash, as a way to play prerecorded tapes in cars.
The tape is arranged in an infinite loop which traverses a central hub and crosses a tape head, usually over a pressure pad to assure proper tape contact. The tape moves at 3¾ inches per second, pulled by tension, but this tension is dampened by a lubricant, usually graphite, on the back of the tape to prevent a tape's tension from damaging the tape and/or player. The tape ends in a Stereo-Pak are not connected by a made of a conductive material — as are the later "automatic" switching 8-track cartridges. 4-track cartridge players had to be switched manually between programs 1 & 2 by a lever on the machine. Due to the method by which the tape is moved, it is impossible to rewind and often risky to fast forward a 4-track tape.
The splices in a 4-track tape can break due to age, handling, or poor manufacturing quality. This problem also affects other endless loop tapes, such as 8-tracks.
The endless loop tape cartridge was designed in 1952 by Bernard Cousino of Toledo, Ohio, around a single reel carrying a continuous loop of standard ¼ inch plastic oxide-coated recording tape running at 3¾ inches/second (9.5 cm/s). Program starts and stops were signalled either by a conductive foil splice or sub-audible tones. The tape was pulled from the center of the reel, passed across the opening at the end of the cartridge and wound back onto the outside of the same reel. The spool itself was freewheeling and the tape was driven only by tension from the capstan. George Eash, also of Toledo, an inventor who had rented space in Cousino's building in the 1950s, later revised Cousino's design (1954, receiving a patent in January 1957) and marketed it under the name Fidelipac. These cartridges were first used in radio stations (broadcast cartridges) from 1959 on to program commercials and single song hits.
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