Enregistrement sonore sur disque de verre

«Le 8 novembre 1888, Berliner fait breveter son invention : le gramophone. En lien avec ce nouvel appareil, il invente également le disque plat ainsi que la matrice pour les imprimer. Sans le savoir, il venait de transformer l'univers de la musique.» Tiré du site Web Musée des ondes Émile Berliner le 28 juillet 2016.
La préservation des enregistrements sonores sur disque présente de multiples défis.
«In late 1934, a new type of instantaneous disc was commercially introduced. It consisted of an aluminum core disc coated with black cellulose nitrate lacquer, although for reasons which are unclear it soon came to be called an "acetate" disc by radio professionals. Later, during World War II, when aluminum was a critical war material, glass core discs were used. A recording lathe and chisel-like cutting stylus like those used to record in wax would be used to engrave the groove into this lacquer surface instead. Given a top-quality blank disc, cutting stylus, lathe, electronics and recording engineer, the result was a virtually noiseless broadcast-quality recording which could be played several times before the effects of wear started to become apparent. The new medium was soon applied to a number of purposes by local stations, but not by the networks, which had a policy against broadcasting prerecorded material and mainly used the discs for archiving "reference recordings" of their broadcasts.
Standard 16 inch transcription discs of the 1930s and 1940s usually held about 15 minutes of audio on each side, but this was occasionally pushed to as much as 20 minutes. Unlike ordinary records, some were recorded inside out, with the start of the recording near the label and the end near the edge of the disc. The label usually noted whether the disc was "outside start" or "inside start". If there was no such notation, an outside start was assumed. Beginning in the mid-1950s, some transcription discs started employing the "microgroove" groove dimensions used by the 12 and 10 inch 33 1/3 rpm vinyl LP records introduced for home use in 1948. This allowed 30 minutes to fit comfortably on each side of a 16 inch disc. These later discs can be played with an ordinary modern stylus or a vintage "LP" stylus. The earlier discs used a larger groove, nearer in size to the groove of a typical 78 rpm shellac record. Using a "78" stylus to play these "standard groove" discs usually produces much better results, and also insures against the groove damage that can be caused by the point of a too-small stylus skating around in the groove and scoring its surface. Some specialist audio transfer engineers keep a series of custom-ground styli of intermediate sizes and briefly test-play the disc with each in order to find the one that produces the best possible results.» Tiré du site Web Wikipedia le 28 juillete 2016.
Pour en connaître davantage sur la préservation de disques de verre, visitez le site North East Document Center.


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