![]() ![]() ![]() ![]() Some transcriptions were recorded with a vertically modulated "hill and dale" groove. Instead of a three-disc set having the 1–2, 3–4 and 5–6 manual sequence, or the 1–6, 2–5 and 3–4 automatic sequence for use with a drop-type mechanical record changer, broadcast sequence would couple the sides as 1–4, 2–5 and 3–6. Although a pair of turntables was used, to avoid any pauses for disc-flipping, the sides had to be pressed in a hybrid of manual and automatic sequencing, arranged in such a manner that no disc being played had to be turned over to play the next side in the sequence. Longer programs, which required several disc sides, pioneered the system of recording odd-numbered sides inside-out and even-numbered sides outside-in so that the sound quality would match from the end of one side to the start of the next. Transcriptions were variously recorded inside out like soundtrack discs (in the era of shellac pressings and steel needles, needle wear considerations dictated an inside start for such a long recording) or with an outside start. 16-inch 33 1⁄ 3 rpm discs playing about 15 minutes per side were used for most of these " electrical transcriptions" beginning about 1930. The desirability of longer continuous playing time soon led to the adoption of the Vitaphone soundtrack disc format. ![]() Syndicated radio programming was distributed on 78 rpm discs beginning in 1928. Like 78s, early soundtrack discs were pressed in an abrasive shellac compound and played with a single-use steel needle held in a massive electromagnetic pickup with a tracking force of five ounces (1.4 N).īy mid-1931, all motion picture studios were recording on optical soundtracks, but sets of soundtrack discs, mastered by dubbing from the optical tracks and scaled down to 12 inches to cut costs, were made as late as 1936 for distribution to theaters still equipped with disc-only sound projectors. Unlike conventional records, the groove started at the inside of the recorded area near the label and proceeded outward toward the edge. Unlike their smaller LP descendants, they were made with the same large "standard groove" used by 78s. The disc diameter was increased to 16 inches (40 cm) and the speed was reduced to 33 1⁄ 3 revolutions per minute. The sound had to play continuously for at least 11 minutes, long enough to accompany a full 1,000-foot (300 m) reel of 35 mm film projected at 24 frames per second. For soundtrack purposes, the less than five minutes of playing time of each side of a conventional 12-inch 78 rpm disc was not acceptable. The prototype of the LP was the soundtrack disc used by the Vitaphone motion picture sound system, developed by Western Electric and introduced in 1926. Neumann lathe with SX-74 cutting head File:Neumann Cutting Machine 03.jpg History Soundtrack discs File:Neumann Cutting Machine 02.jpg The use of the word "album" persisted for the one-disc LP equivalent. Previously, such collections, as well as longer classical music broken up into several parts, had been sold as sets of 78 rpm records in a specially imprinted "record album" consisting of individual record sleeves bound together in book form. Only the microgroove standard was new, as both vinyl and the 33 1⁄ 3 rpm speed had been used for special purposes for many years, as well as in one unsuccessful earlier attempt to introduce a long-playing record for home use by RCA Victor.Īlthough the LP was suited to classical music because of its extended continuous playing time, it also allowed a collection of ten or more pop music recordings to be put on a single disc. Each side of a 12-inch LP could play for about 22 minutes. The new product was a 12- or 10-inch (30 or 25 cm) fine-grooved disc made of PVC ("vinyl") and played with a smaller-tipped "microgroove" stylus at a speed of 33 1⁄ 3 rpm. At the time the LP was introduced, nearly all phonograph records for home use were made of an abrasive (and therefore noisy) shellac compound, employed a much larger groove, and played at approximately 78 revolutions per minute (rpm), limiting the playing time of a 12-inch diameter record to less than five minutes per side. ![]()
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