The AES coarse-groove

calibration In measurement technology and metrology, calibration is the comparison of measurement values delivered by a device under test with those of a calibration standard of known accuracy. Such a standard could be another measurement device of known ...

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 Mass transfer is the net movement of mass from one location (usually meaning stream, phase, fraction, or component) to another. Mass transfer occurs in many processes, such as absorption, evaporation, drying, precipitation, membrane filtra ...

of coarse-groove records to

digital media In mass communication, digital media is any media (communication), communication media that operates in conjunction with various encoded machine-readable data formats. Digital content can be created, viewed, distributed, modified, listened to, an ...

, much like using a photographic calibration reference in image work.

Libraries A library is a collection of Book, books, and possibly other Document, materials and Media (communication), media, that is accessible for use by its members and members of allied institutions. Libraries provide physical (hard copies) or electron ...

and archives around the world have collections of many thousands of coarse-groove mechanical audio recordings,

phonograph A phonograph, later called a gramophone, and since the 1940s a record player, or more recently a turntable, is a device for the mechanical and analogue reproduction of sound. The sound vibration Waveform, waveforms are recorded as correspond ...

gramophone record A phonograph record (also known as a gramophone record, especially in British English) or a vinyl record (for later varieties only) is an analog sound storage medium in the form of a flat disc with an inscribed, modulated spiral groove. The g ...

s, largely 78s or 78

revolutions per minute Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or r⋅min−1) is a unit of rotational speed (or rotational frequency) for rotating machines. One revolution per minute is equivalent to hertz. Standards ISO 80000-3:2019 de ...

(rpm) discs. This is a substantial recorded heritage of mankind's music and

spoken word Spoken word is an oral poetic performance art that is based mainly on the poem as well as the performer's aesthetic qualities. It is a 20th-century continuation of an oral tradition, ancient oral artistic tradition that focuses on the aesthetic ...

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 Plastics are a wide range of synthetic or semisynthetic materials composed primarily of polymers. Their defining characteristic, plasticity, allows them to be molded, extruded, or pressed into a diverse range of solid forms. This adaptab ...

used in their manufacture are deteriorating slowly but steadily.

Preservation Preservation may refer to: Heritage and conservation * Preservation (library and archival science), activities aimed at prolonging the life of a record while making as few changes as possible * ''Preservation'' (magazine), published by the Nat ...

programs have been underway by a number of organizations. Decreasing costs of

digital storage Data storage is the recording (storing) of information (data) in a storage medium. Handwriting, Phonograph record, phonographic recording, magnetic tape, and optical discs are all examples of storage media. Biological molecules such as RNA ...

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 The Audio Engineering Society (AES) is a professional body for engineers, scientists, other individuals with an interest or involvement in the professional audio industry. The membership largely comprises engineers developing devices or product ...

(AES) to provide a calibration tool for standard transfer of mechanical coarse-groove audio recordings from the analog to the digital domain.

Specifications

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.)

A Closer Look At The Preservation Problem

According to Ted Kendall, maker of the Front End audio restoration unit also known as "The Mousetrap", the equalization time constants for post-1955 78s used in the Front End are 3180/450/50 ms. These time constants are identical to those used in the AES Coarse-groove Calibration Discs. Since the 78 rpm record would be

obsolete Obsolescence is the process of becoming antiquated, out of date, old-fashioned, no longer in general use, or no longer useful, or the condition of being in such a state. When used in a biological sense, it means imperfect or rudimentary when comp ...

by 1960, this means that there is a very large population of pre-1955 78s requiring different equalization settings depending on the vintage and label of the disc. :''Type of Recording: Equalizer Settings'' :Acoustic recordings (pre-1925): Flat/AC/AC :FFRR 78s: Flat/636/25 :EMI 78s 1945-1955: Flat/636/Flat :Most other UK 78s 1925-1945: Flat/531/Flat :Post-1955 78s: 3180/450/50 :BBC direct recordings 1945-1960: Flat/BBC/BBC :CCIR standard coarse-groove transcriptions: Flat/450/50 :AES (some early US Lps): Flat/400/63.6 :Modern LPs (RIAA equalization): 3180/318/75 :Lateral cut NAB transcriptions: 2250/250/100 :Vertical cut NAB transcriptions: Flat/531/40* :Western Electric 78s: Flat 531/Flat* :*Adjustments needed* So, the dilemma is this: should coarse-groove recordings be transferred in mass to digital using an arbitrary phonoequalization curve such as with the AES calibration discs, or should each recording be matched to the curve appropriate to its vintage and label, then transferred to digital media?

Use of RIAA Equalization

Because the

RIAA equalization RIAA equalization is a specification for the recording and playback of phonograph records, established by the Recording Industry Association of America (RIAA). The purposes of the equalization are to permit greater recording times (by decreasi ...

standard has been in use internationally for

records since 1953 and is based on recording practices used for many years by RCA Victor, a dominant record producer, the electronics needed for this purpose are as readily available as

record players A phonograph, later called a gramophone, and since the 1940s a record player, or more recently a turntable, is a device for the mechanical and analogue reproduction of sound. The sound vibration waveforms are recorded as corresponding phys ...

are. For vintage recordings the Esoteric Sound Re-Equalizer can readily be connected as a standard item to the record playback equipment. The Re-Equalizer is used to modify RIAA. Then, depending on the vintage and label of the 78 rpm record, the appropriate equalizer bass turnover and treble rolloff settings can be easily looked up in a reference guide.

Other Equipment

Another approach to obtaining the right phonograph record equalization settings for transferring vintage recordings to digital media is to use the Chronologic Equalizer in the Souvenir Vintage Sound Processor – MK-2 made by K-A-B Electronics.K-A-B Electronics P. O. Box 2922, Plainfield, New Jersey 07062-0922 :''Equalizer Setting'' :AC: Acoustic recordings :AE: Early electric recordings; Victor (some 1925), Columbia (1925), and most European to 1955 :E3: Recordings with a 300 Hz turnover; Columbia (1925-1938), and FRR to 1955 :E5: Recordings with a 500 Hz turnover; Victor (most 1925-1952) :E7: Recordings with a 700 Hz turnover (some NBC Orthacoustic transcriptions) :CO: Columbia 78 curve (1938 to 1955) :TR: Transcriptions (NAB) :MO: RIAA equalization

Notes

{{Reflist Audio engineering Broadcast engineering Sound technology Audio storage