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 know ...

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 filtration, ...

of coarse-groove records to

digital media Digital media is any communication media that operate in conjunction with various encoded machine-readable data formats. Digital media can be created, viewed, distributed, modified, listened to, and preserved on a digital electronics device. ' ...

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

Libraries A library is a collection of materials, books or media that are accessible for use and not just for display purposes. A library provides physical (hard copies) or digital access (soft copies) materials, and may be a physical location or a vir ...

and

archives An archive is an accumulation of historical records or materials – in any medium – or the physical facility in which they are located. Archives contain primary source documents that have accumulated over the course of an individual or ...

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

phonograph A phonograph, in its later forms also called a gramophone (as a trademark since 1887, as a generic name in the UK since 1910) or since the 1940s called a record player, or more recently a turntable, is a device for the mechanical and analogu ...

gramophone record A phonograph record (also known as a gramophone record, especially in British English), or simply a record, is an analog sound storage medium in the form of a flat disc with an inscribed, modulated spiral groove. The groove usually starts nea ...

s, largely 78s or 78

revolutions per minute Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or with the notation min−1) is a unit of rotational speed or rotational frequency for rotating machines. Standards ISO 80000-3:2019 defines a unit of rotation as the dimensionl ...

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

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

made over a period of 65 years. The 78 rpm disc was largely out of

production Production may refer to: Economics and business * Production (economics) * Production, the act of manufacturing goods * Production, in the outline of industrial organization, the act of making products (goods and services) * Production as a stati ...

by 1960. These mechanical recordings won't be available indefinitely since the

plastics Plastics are a wide range of synthetic polymers, synthetic or semi-synthetic materials that use polymers as a main ingredient. Their Plasticity (physics), plasticity makes it possible for plastics to be Injection moulding, moulded, Extrusion, e ...

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, phonographic recording, magnetic tape, and optical discs are all examples of storage media. Biological molecules such as RNA and DNA are consi ...

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 products ...

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

analog Analog or analogue may refer to: Computing and electronics * Analog signal, in which information is encoded in a continuous variable ** Analog device, an apparatus that operates on analog signals *** Analog electronics, circuits which use 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 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, in its later forms also called a gramophone (as a trademark since 1887, as a generic name in the UK since 1910) or since the 1940s called a record player, or more recently a turntable, is a device for the mechanical and analogu ...

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 Roll-off is the steepness of a transfer function with frequency, particularly in electrical network analysis, and most especially in connection with filter circuits in the transition between a passband and a stopband. It is most typically app ...

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