Denne lenken går direkte til EQ-historien. And it's a bloody mess, helt fram til 1980-tallet:
en.wikipedia.org
Ser den...@Valentino, men det var noe annet enn avtastning med "stift".
In 1926
Joseph P. Maxwell and Henry C. Harrison from Bell Telephone Laboratories disclosed that the recording pattern of the Western Electric "rubber line" magnetic disc cutter had a constant velocity characteristic. This meant that as frequency increased in the treble, recording amplitude decreased. Conversely, in the bass as frequency decreased, recording amplitude increased.
Therefore, it was necessary to attenuate the bass frequencies below about 250 Hz, altså nermest det motsatte av riaa, the bass turnover point, in the amplified microphone signal fed to the recording head. Otherwise, bass modulation became excessive and overcutting took place into the next record groove.
When played back electrically with a magnetic pickup having a smooth response in the bass region, a complementary boost in amplitude at the bass turnover point was necessary. G. H. Miller in 1934 reported that when complementary boost at the turnover point was used in radio broadcasts of records, the reproduction was more realistic and many of the musical instruments stood out in their true form