Magnetic cartridge

A magnetic cartridge (phono cartridge) is a type of transducer used in the playback of analog sound recordings called records on a record player, now commonly called a turntable because of its most prominent component but formally known as a phonograph in the US and a gramophone in the UK.

A cartridge, also known as a pickup is an electro-mechanical device which converts vibrational energy into electrical energy. The cartridge contains a removable or permanently mounted stylus, the tip of which makes physical contact with a record groove. (In popular usage and in disc jockey jargon, the term needle, is often used in place of stylus.) An electrical signal created in the cartridge can then be amplified and then converted into sound by a loudspeaker.

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 the 1890s. 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type of magnetic pickup completely dominated the market well into the 1930s, but by the end of that decade it had been superseded by a comparatively lightweight piezoelectric crystal pickup type.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.

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