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Converting 78 Records  (June 2017)


Stereo, Not Mono

Conventional wisdom advises capturing mono records in mono, as this increases the recording’s dynamic range (difference between the loudest and softest passages).  Based on my own experiences with waveform editing, however, I have long since abandoned this approach and always capture 78s, as well as LPs and 45s, in stereo for the following reason.


While performing waveform editing on mono records captured in stereo, I discovered that pops aren’t identical in the left and right channels.  One is often larger than the other, and sometimes the pop occurs in only one of the channels (note the image below, where a pop occurs only in the left [upper] channel).  This might occur if the tonearm was bumped during playing and scratched the record in one direction, such as toward the record’s center.


In the case of a one-channel pop, I can replace the pop with the music from the other channel (technically speaking, muting the pop in one channel and then mixing the two channels at 100% each).  While the music replacing the pop may not be exactly identical to the music that the pop destroyed, it’s a lot closer than the pop was.  The same process can be used to replace the more severe pop in one channel with its less severe sibling from the other, and this provides a better starting point for removing the pop altogether from both channels.

Speed Correction

Before 1925, recording speeds varied between 60 and 130 rpm.  Some record companies accommodated consumers by etching the appropriate speed on the lead-out portion of the record, and the gramophone’s speed could be adjusted accordingly.


Beginning in 1925, electric record players with synchronous motors were introduced as electricity became widely available in the U.S.  As they became common, American record companies adopted 78.26 rpm as the standard speed (with 60 Hz current, the motor turns at 3,600 rpm, and using a 46:1 gear ratio yields 78.26 rpm).  In other countries that had major record producers, the available current was 50 Hz, and the standard that emerged was 77.92 rpm (derived from a motor turning at 3,000 rpm and using a 77:2 gear ratio).


Since my turntable’s 78 speed is not adjustable, I convert 78s at 78.26 rpm.  If I can identify the country of origin, or if a speed other than 78.26 is etched on the record, I can use software to adjust the pitch (and concomitantly the length of the track) to sound like the record was being played at the intended speed.


Recommendation for Noise Reduction

Most 78s were made of shellac, with ground slate added to strengthen records so they would stand up to gramophone tonearms where tracking weight was measured in ounces instead of grams.  During playing, the gramophone needle not only vibrated in reaction to what was on the groove walls (which produced the sound), it also scraped particles of the slate filler out of the shellac, leaving them behind in the grooves.  Even after cleaning, 78s will have a characteristic crackle that persists throughout the entire record.  (In contrast, the numerous clicks one hears on a well-used vinyl LP are caused by needle drops rather than dislodged vinyl particles and usually appear just at the beginning of each side.)  Because crackle is almost always present in 78s, Noise Reduction is highly recommended.



Please see the Equalization article; treatment of 78s is extensively discussed there.

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