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The Edison Diamond Disc Record is a type of phonograph record marketed by Thomas A. Edison, Inc. on their Edison Record label from 1912 to 1929. They were named Diamond Discs because the matching Edison Disc Phonograph was fitted with a precision-made semi-permanent diamond stylus for playing them. Diamond Discs were incompatible with ordinary disc record players, the disposable steel needles of which would damage them while extracting hardly any sound. Uniquely, they are about 1/4 inch (6 mm) thick. Edison had previously made only phonograph cylinders but decided to add a disc format to the product line because of the increasingly dominant market share of the shellac disc records (later called "78s" because of their typical rotational speed) made by competitors such as the Victor Talking Machine Company. Victor and most other makers recorded and played sound by a lateral or side-to-side motion of the stylus in the record groove, while in the Edison system the motion was vertical or up-and-down, known as "hill-and-dale" recording, as used for cylinder records. An Edison Disc Phonograph is distinguished by the diaphragm of the reproducer being parallel to the surface of the record. The diaphragm of a reproducer used for playing ordinary records is at a right angle to the surface. In 1929 Edison also produced a short-lived series of ordinary thin lateral-cut "needle type" disc records. ==History == The grooves on an Edison Disc are smooth on the sides and have a variable depth. Standard lateral discs will have a more constant depth, but the sides of the groove are scalloped. As the Edison groove pitch (or "TPI", i.e. "threads per inch") was 150, a much finer grooving than that on lateral discs, Edison's 10-inch discs played considerably longer than Victor's or Columbia's -- up to nearly five minutes per side. The Edison Disc is also ¼-inch thick (supposedly to prevent warping), and was filled with wood flour, and later, china clay.〔(【引用サイトリンク】title=Tim Gracyk's Phonographs, Singers, and Old Records -- Edison Diamond Discs: 1912 - 1929 )〕 Victor's system could not play Edison Discs as the needles used would cut through the recorded sound, and the Edison system could not play Victor or other lateral discs unless one used special equipment, like the Kent adapter. There is an example of a device to play Edison discs on a Victor machine.〔(【引用サイトリンク】title=Very rare reproducer made for Victrola machines to play Edison DD records. )〕 The Brunswick Ultona and the Sonora Phonograph were the only machines besides the Diamond Disc player that could play Diamond Discs, but Edison made an attempt at curbing this (a phonograph/gramophone that could play Edison, Victor/lateral 78s, and Pathé discs) by stating "This Re-Creation should not be played on any instrument except the Edison Diamond Disc Phonograph and with the Edison Diamond Disc Reproducer, and we decline responsibility for any damage that may occur to it if this warning is ignored."〔(【引用サイトリンク】title=Tim Gracyk's Phonographs, Singers, and Old Records -- Brunswick Phonographs and Records )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Edison Disc Record」の詳細全文を読む スポンサード リンク
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