The Swezey Digital Filter

Fixed Equalization of 78 RPM Phonograph Recordings

Since the 1950's phonograph records are recorded using the Recording Industry Association of America (RIAA) equalization curve.
Lower frequencies are reduced and higher frequencies are increased when the record is actually cut.
Modern phonographs reverse this curve during playback to restore the proper original levels.
Unfortunately nearly all 78 RPM records predate this and did not follow this curve.
As a result when they are played back their low frequencies are falsely boosted and high frequencies reduced.
In addition most 78s after 1925 used their own proprietary equalization curves.
These vary by manufacturer and recording date and have names like Victor 1925, Columbia 1937, RCA 1938 and Capitol 1942.
The program can undo the RIAA curve and allow you to select from a list of predefined curves or set equalization parameters manually.
The program is defaulted to use RCA 1938, which works pretty well for most 78s.
Below is a brief excerpt from Decca Record 24508-B A Bluebird Singing in My Heart with Bing Crosby

To hear (or download) the uncorrected "before" version Click Here!
To hear (or download) the corrected "after" version Click Here!
Both excerpts are MPEG mp3 audio files. If you need help playing these files Click Here!

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(c) 2007, Thomas F. Swezey. All rights reserved.