The rated output of a cartridge (such as 3.0 mV, or 0.5 mV) is the voltage of the output signal, usually based on the stylus tracking at a specific rate (for example, 5 cm per second). Moving coil cartridges usually have voltage output of less than 1.0 mV (although there are a few "high output" MC cartridges with output of 1.5 mV or so). Moving magnet cartridges usually have output levels in the 3-6 mV range (although a few may run higher).
The output level of the cartridge will determine how much gain, measured in dB, that must be provided by the phono preamp or step-up transformer. Usually, moving coil cartridges need about 60dB of gain from the phono preamp (before the signal goes to the main preamp), and moving magnet cartridges usually need around 35-40 dB of gain from the phono preamp.
The voltage needed to drive your main power amp is determined by the output voltage of the linestage preamp, not the output of the cartridge / phono preamp combo.
The output level of the cartridge will determine how much gain, measured in dB, that must be provided by the phono preamp or step-up transformer. Usually, moving coil cartridges need about 60dB of gain from the phono preamp (before the signal goes to the main preamp), and moving magnet cartridges usually need around 35-40 dB of gain from the phono preamp.
The voltage needed to drive your main power amp is determined by the output voltage of the linestage preamp, not the output of the cartridge / phono preamp combo.