WAMS at SlumberTech!
Record Equalization
By Russell Fisher

The following charts provide the equalization curves required for the accurate playback of early LPs and all electrical 78s. Starting in 1955, all LPs use the standard RIAA curve, which is built into all new preamplifiers. Acoustic 78s were made without any equalization.

Use of these equalization curves during playback requires either an older preamp or a specialized equalizer such as the WaxWorks II Restoration Module. The equalization can also be roughly approximated with a graphic/octave equalizer.

This information is taken from several sources: the "Dial Your Discs" chart which appeared in High Fidelity magazine during the early 1950s, the chart provided by Owl Audio, the chart compiled by James R. Powell, Jr. and published in the ARSC Journal, and the jackets of various early LPs.

"Turnover" (col. 2) is the frequency below which the record manufacturer diminished the bass when mastering the disc, requiring a corresponding boost during playback. In the chart, turnover is stated using the name of the recording curve, as given on most older preamps; a list of these curves and their turnover frequences is at the end of the chart. Where a specific turnover is not available on the Owl I, the preferred setting is given in parentheses.

"Rolloff" (col. 3) is the amount of treble cut at 10 KHz required during playback to compensate for preemphasis added during disc mastering. In the chart, rolloff is stated in dB; where a specific rolloff is not available on the Owl 1, the preferred setting is given in parentheses.

These are the "official" equalizations, but there may be considerable variation from one company (or disc) to another, especially with 78s. Adjustments can be made using the tone controls or even alternate equalization curves: increase turnover if the bass sounds too thin, and Increase rolloff if the treble is too strong.

Equalization Chart for Pre-1955 LP Records

                              Turnover          Rolloff
     Angel                       NAB            -12 dB
     Audio Fidelity              NAB            -16 dB
     Bach Guild (501-529)        NAB            -16 dB
     Bartok 301-304, 309,
       906-920                   629 Hz (500)   -16 dB
     Boston                      COL            -16 dB
     Caedmon 1001-1022           629 Hz (500)   -16 dB
     Capitol                     AES            -12 dB
     Capitol-Cetra               AES            -12 dB
     Cetra-Soria                 COL            -16 dB
       or                        AES            -12 dB
     Colosseum                   AES            -12 dB
       or                        COL            -16 dB
     Columbia                    COL            -16 dB
     Concert Hall                AES            -12 dB
       or                        COL            -16 dB
       or (until 1954)           RIAA           -8.5 dB
     Decca                       AES            -12 dB
     Decca (until 11/55)         COL            -16 dB
     Decca FFRR (1951)           300 Hz (250)   -14 dB
     Decca FFRR (1953)           450 Hz (500)   -11 dB (-8.5)
     Ducretet-Thomson            450 Hz (500)   -11 dB (-8.5)
     EMS                         375 Hz         -12 dB
     Epic (until 1954)           COL            -16 dB
     Esoteric                    AES            -12 dB
     Folkways                    COL            -16 dB
     Haydn Society               COL            -16 dB
     HMV                         COL            -16 dB
     London (up to LL-846)       450 Hz (500)   -11 dB (-8.5)
     London International        450 Hz (500)   -11 dB (-8.5)
     Lyrichord                   COL            -16 dB
          or                     AES            -16 dB
          new:                   629 Hz (750)   -16 dB
     Mercury (until 10/54)       AES            -12 dB
     MGM                         NAB            -12 dB
     Oceanic                     COL            -16 dB
     Oiseau-Lyre (until 1954)    COL            -8.5 dB
     Overtone                    NAB            -16 dB
     Polymusic                   NAB            -16 dB
     RCA Victor (until 8/52)     NAB            -12 dB
     Remington                   NAB            -16 dB
     Urania (most)               COL            -16 dB
     Urania (AES eq)             AES            -12 dB
     Vanguard (411-22, 6000-18)  COL            -16 dB
     Vox (until 1954)            COL            -16 dB
     Westminster (before 1956)   NAB            -16 dB
       or                        AES            -12 dB

Equalization Chart for 78 rpm Records

                              Turnover          Rolloff
     Acoustics                   0               0 dB
     Brunswick                   NAB             0 dB
     Capitol (1942)              AES            -12 dB
     Columbia (1925)             200 Hz (250)   -7 dB (-8.5)
     Columbia (1938)             300 Hz (250)   -16 dB
     Columbia (Eng.)             250 Hz          0 dB
     Decca (1934)                AES            -12 dB
     Decca FFRR (1949)           250 Hz         -5 dB
     early 78s (mid-'30s)        NAB             0 dB
     EMI (1931)                  250 Hz          0 dB
     HMV (1931)                  250 Hz          0 dB
     London FFRR (1949)          250 Hz         -5 dB
     Mercury                     AES            -12 dB
     MGM                         RIAA           -12 dB
     Parlophone                  NAB             0 dB
     Victor (1925)               200-500 Hz     -7 dB (-8.5)
     Victor (1938-47)            NAB            -7 dB (-8.5)
     Victor (1947-52)            NAB            -12 dB

Equalization Curves by Name

                                Turnover        Rolloff
     AES                         400 Hz  (375)  -12 dB
     FFRR (1949)                 250 Hz         -5 dB
     FFRR (1951)                 300 Hz  (250)  -14 dB
     FFRR (1953)                 450 Hz  (500)  -11 dB (-8.5)
     LP/COL                      500 Hz*        -16 dB
     NAB                         500 Hz         -16 dB
     Orthophonic (RCA)           500 Hz         -11 dB (-8.5)
     629                         629 Hz  (750)
     RIAA                        500 Hz**       -13.7 dB
* modified from NAB: less bass below 150 Hz, requiring about 3dB boost with bass tone control.

** "Very close" to NAB.

Return to the WAMS at SlumberTech Homepage