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Challenges in Optical Recovery of Otherwise Unplayable Analogue Audio Disc Records

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Though limited to monophonic playback, the INA-Saphir analogue disc recording optical playback system is applicable to a wide range of grooved disc records, from earliest lateral and vertical-cut shellacs to recorded letters, from glass-based discs with missing chunks to thin transparent dual-side records and phonocards. The effort required for playing a disc side mostly depends on the number of cracks or missing parts. The current operating mode consists in delegating to a software solver the identification of the best path across all the groove track fragments, manually adjusting the details, and iterating until the satisfying solution is found. This process, from straightforward on records with few cracks, may spill over several days when extracting in parallel the full contents of several records with many wide cracks. The achievable quality is quite variable, very much dependent on the reflectivity of the groove walls. When the condition of the record does not allow wet cleaning, dry cleaning is still often possible. Dry-cleaning using roller brushes is applicable to removing the largest part of lacquer plasticizer exudates. In the case of de-laminating lacquer flakes, a hand-held soft motorized rotary brush can still be applied by maintaining the lacquer flakes in place with a hand-held soft window, and re-positioning the flakes before scanning under a glass pane. The scanner is compact, similar in size to most conventional turntables, still can accommodate up to 17 Inch discs, and allows recovering audio signals up to 20kHz. It can be moved easily, and can be operated without complex setup. Improvements on the software are still underway, but the system can already be replicated and made available to audio archives and service providers.

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