Audio Engineering Society, Coarse-groove Calibration Discs

Audio Engineering Society, Coarse-groove Calibration Discs

Libraries and archives around the world have collections of many thousands of coarse-groove mechanical audio recordings, phonograph or gramophone records, largely 78s or 78 rpm discs. This is a substantial recorded heritage of mankind's music and spoken word made over a period of 65 years. The 78 rpm disc was largely out of production by 1960. These mechanical recordings won't be available indefinitely since the plastics used in their manufacture are deteriorating slowly but steadily. Preservation programs have been underway by a number of organizations. Decreasing costs of digital storage media now make it possible to consider all mechanical audio recordings for transfer to the digital domain. Thus a widespread need was recognized by the Audio Engineering Society (AES) to provide a calibration tool for standard transfer of mechanical coarse-groove audio recordings from the analog to the digital domain.

The AES coarse-groove calibration discs (AES-S001-064) are a boxed set of two identical discs, one for routine use, one for master reference. The intent is to characterize the reproduction chain for the mass transfer of coarse-groove records to digital media, much like using a photographic calibration reference in image work.

Side A:

Gliding tone, 20 Hz to 20 kHz

Speed: 77.92 rpm

Lateral (mono) coarse groove

Time constants: 3180/450/0 ms

Separate outer & inner bands:

1 kHz trigger tone

Gliding tone, 20 Hz to 20 kHz

1 kHz reference level*

*20 mm Light Band Width (LBW);

approx 8 cm/s peak-to-peak, 5.7 cm/s rms

Side B:

Single tones, 18kHz to 30 Hz

Speed: 77.92 rpm

Lateral (mono) coarse groove

Time constants: 3180/450/50 ms

(Pressed under license from EMI Records Ltd.)