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Gramophone - Historical recordings from the Swiss National Sound Archives

THE TASK OF SAFEGUARDING

Copying (analysis and analog to digital conversion)

Once the washing phase is concluded, the disc moves on to the audio studio, where it is examined under a microscope to determine the dimensions and shape of the groove and to verify the physical state of its surface. These measurements and checks allow us to choose the most suitable stylus for playing the disc. The indications on the label (brand, catalog and matrix numbers) allow us to set the equalization and rotation speed correctly. Lastly, in difficult cases, to obtain even better results, the geometry of the reading arm is optimized.

The turntable signal is converted from analog to digital and "leveled" to ensure the best dynamics and signal/interference relationship. The digital signal is recorded on high resolution WAV files. Those files will contain only what is extracted from a single document (disc or set of discs), and they will be considered as the first generation "archival copy". Any subsequent copying or processing will be derived from this copy.

All the working phases, as well as the equipment used and the adjustments made are documented to allow the exact copying process to be reconstructed even in the future. The time necessary to copy a 78 rpm disc can be quantified as 4 times the total duration of the disc. On average, therefore, considering a duration of 8 min for both sides, it takes about 30 minutes of working time.

The copying process for the cylinders is very similar to that of the 78rpm records. The only major difference concerns the size and shape of the groove, which are limited to 2-3 different types and that generally no equalization is applied.

Disc

Copying

Cylinder

Copying



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