Definição do conceito
[ENG] 80 rpm | Edison Records Diamond Disc label, early 1920s. Edison Disc Records always ran at 80 rpm. | SOURCE : Phonograph record. in: WIkipedia. Available at : https://en.wikipedia.org/wiki/Phonograph_record Accessed : 20 sep. 2022
=====================================
[ENG] 80 rpm | Earliest speeds of rotation varied widely, but by 1910 most records were recorded at about 78 to 80 rpm. In 1925, 78.26 rpm was chosen as a standard for motorized phonographs, because it was suitable for most existing records, and was easily achieved using a standard 3600-rpm motor and 46-tooth gear (78.26 = 3600/46). Thus these records became known as 78s (or "seventy-eights"). This term did not come into use until after World War II when a need developed to distinguish the 78 from other newer disc record formats. Earlier they were just called records, or when there was a need to distinguish them from cylinders, disc records. | .../... | The acoustical era: 1877–1925 | ... Recording and playing speeds ranged from 72 to 86 rpm before the standard settled at 78 (though Columbia, for example, issued 80 rpm discs for some time after 1920). | SOURCE : Yale UNIVERSITY LIBRARY - Irving S. Gilmore Music Library Available at : https://web.library.yale.edu/cataloging/music/historyof78rpms Accessed : 20 sep. 2022
=====================================
[ENG] 80 rpm | 45s: (c. 1949 - 1990) | Does anyone know why 78 revolutions per minute was chosen as the standard rotation speed of old-fashioned gramophone records, rather than a round number such as 75 or 80 rpm? And are there convincing explanations for the choice of speeds for later EPs and LPs of 33 1/3 rpm and 45 rpm? | It was Emil Berliner, the inventor of the gramophone, who determined roughly how fast old disc records should spin. He avoided Edison´s need for a stylus made from precious jewels by using points which could be made from steel sewing needles and pins. The size of the stylus effectively determined the size of the grooves in a record and the recordable frequency range limited by this groove size determined a speed between 70 and 90 rpm. | Standardization did not begin until 1912, when the British Gramophone Company conducted listening tests on their back catalogue. They settled on the average (or possibly the median) of these tests, which turned out to be 78 rpm. Other companies adopted this, but the process was not complete until the early 1930s. Even after this date Òrogue rpmÓ records still appeared. After standardization problems still occurred. Because of electrical mains frequencies differences on opposite sides of the Atlantic, stroboscopic speed testers and synchronous motors meant a nominal speed of 77.922 rpm in countries that used 50 hertz and 78.261 in countries that used 60 hertz. These were later fixed in national (but not international) standards. | SOURCE: Why 78, 45 and 33 1/3 record formats? Available at : https://www.history-of-rock.com/record_formats.htm Accessed : 20 sep. 2022
=====================================
