Electronics for Vinyl

Chapter 7

RIAA Equalisation

Equalisation and Its Discontents

Both moving-magnet and moving-coil cartridges operate by the relative motion of conductors and magnetic field, so the voltage produced is proportional to rate of change of flux. The cartridge is therefore sensitive to groove velocity rather than groove amplitude, and so its sensitivity is expressed as X mV per cm/sec. This velocity- sensitivity gives a frequency response rising steadily at 6 dB/octave across the whole audio band for a groove of constant amplitude.

The RIAA replay equalisation curve is shown in Figure 7.1. It has three basic corners in its response curve, with frequencies at 50.05 Hz, 500.5 Hz, and 2.122 kHz, which are set by three time-constants of 3180 µsec, 318 µsec, ...