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magnetic cartridge
A magnetic cartridge is a transducer used for the playback of gramophone records on a turntable or phonograph. It is a mechanical device that converts vibrational energy from a stylus riding in a record groove into an electrical signal that is subsequently passed through amplification and then converted into sound energy by a loudspeaker system.
== History ==
The first commercially successful type of electrical phonograph pickup was introduced in 1925. Although electromagnetic, its resemblance to later magnetic cartridges is remote: it contained a bulky horseshoe magnet and employed the same imprecisely mass-produced single-use steel needles which had been standard since the first crude disc record players appeared in 1906. Its tracking weight was specified in ounces, not grams. This early type of magnetic pickup completely dominated the market well into the 1930s, but by the end of that decade it had been superseded by a comparatively lightweight piezoelectric crystal pickup type. The use of short-lived disposable metal needles remained standard. During the years of affluence and long-deferred consumer demand immediately following World War II, as old record players with very heavy pickups were replaced, precision-ground and conveniently long-lasting stylus tips made of sapphire or exotic hard metals such as osmium were increasingly popular. However, records made for home use still played at 78 rpm and most of them were still made of the same old abrasive shellac compound formulated to rapidly wear down the points of steel needles to fit the groove.
The introduction of the 33 rpm vinyl LP "album" in 1948 and the 45 rpm vinyl "single" in 1949 prompted consumers to upgrade to a new multi-speed record player with the required smaller-tipped "microgroove" stylus. Sapphire and diamond then became the standard stylus tip materials. At first, the new styli came installed in smaller, lighter piezoelectric crystal or ceramic cartridges of the general type found in inexpensive self-contained portable record players throughout the vinyl era. Ceramic cartridges continue to be used in most of the "retro" and compact record players currently being made, in part because they are comparatively robust and resistant to damage from careless handling, but mostly because they are cheaper. However, during the 1950s, a new generation of small, lightweight, highly compliant magnetic cartridges appeared and quickly found favor among high-fidelity enthusiasts because of their audibly superior performance. The high compliance also reduced record wear. They soon became standard in all but the cheapest component audio systems and are the most common type of pickup cartridge in use today.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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