EQ Curves

 

EQ Curves

In order to create records in the first place, adjustments had to be made to compensate for the lack of surface space on a record.  Because records rely on grooves, in order to accurately relay Bass passages on a record, the grooves would need to be so far apart that in many cases it would be impossible to fit a full song on a 78 or more than one or two on an LP.  In order to compensate, records were designed minus a great deal of the Bass and manufacturers depended on the equipment that they were played on to add that bass back into the file during the listening process. 

An EQ Curve is simply a preset equalizer that says, "I know you're going to be missing these frequencies...I'll just put them back in automatically."

The RIAA curve was designed for LPs and 45s.  Almost all modern preamps or stereo systems add this RIAA curve in one respect or another on playback.  In the heyday of turntables and stereo systems, many folks would shop for hours until they found the stereo system that sounded best.  Because all stereos sounded differently, this can let you know just how well this RIAA curve was followed.  Each company interpreted these EQ settings with their own style.  While this was good for listening, it may not be the best for today's technology.  If you are mainly transferring LPs and 45s to the computer, you may want to read about the CTP1000 Flat Phono Preamp Series.  Just Click Here.

78 records were designed differently and require a different set of equalizer settings in order to play them accurately. 

Verify that you are utilizing the correct equalization curve for the particular type and brand of record that you are about to transfer.  Turnover and sometimes Roll-off are critical breakpoint frequencies that must be matched in a complementary manner to the recording process in order to preserve the "flat" response of the original recording session.  Turnover frequencies for electrical recordings are between 200 to 500 Hertz, and are in the 5 KHz region of the audio spectrum.  Acoustical recordings should always be transferred "flat" and "electricals" should be transferred with equalization that is the correct inverse of the recording equalization that was used in the mastering process.  There are tables of values available to determine the correct values for this.  Also, it is important to have a pre-amplifier that has the ability to adjust the turnover and Roll-off frequencies.  For more information on this topic, refer to the section entitled "Record Transfer to Hard Drive Technical Hints."  Below is a list of common Turnover Frequencies for some of the more common brands of lateral cut 78-RPM records:

Type, Brand, or Process Turnover Frequency
   
Acoustical Recordings 0 Hz
   
Columbia (1925 - 1937) 200 Hz
Victor (1925 - 1937) 200 Hz
Westrex 200 Hz
   
Decca (1935 - 1949) 250 Hz
EMI 250 Hz
English Columbia 250 Hz
HMV (1931) 250 Hz
EMI (1931) 250 Hz
London 250 Hz
Blumlein 250 Hz
   
Columbia (1938 End) 300 Hz
   
BSI 350 Hz
   
Capitol 400 Hz
Mercury 400 Hz
   
Brunswick 500 Hz
Decca (1925 1929) 500 Hz
Edison Laterals (1929) 500 Hz
MGM 500 Hz
Parlophone 500 Hz
Victor (1938 1952) 500 Hz
   
629 629 Hz