Noise of MM Cartridges

Abstract

The design of hum- and noiseless RIAA pre-amplifiers is really a kind of art. The existence of a great variety of circuit designs tells many stories about chases after high signal-to-noise ratios (SN), overload matters, and fights for precision of the RIAA transfer. Solutions proposed in the past to use – as substitute – resistors or inductors1 at the input of a RIAA amplifier for noise measurement purposes or to set on mathematical octave-band analysis2 to get SN results close to the measured ones (with MM cartridge as input load) do not satisfy. In addition, hum spoils many measurement attempts and the optimal loading capacitance of the MM cartridge is quite often not taken into account of calculations or measurements.