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There are two primarily used phono cartridge types that use magnetic techniques to generate the electrical signal used by an audio preamplifier. Moving Coil cartridges generally produce much lower output levels than moving magnet designs. For example, a common MC cartridge generates around 500 uVolts at 1 kHz with a reference test record (Hi Fi News). That is much lower than the output of a moving magnet cartridge (MM) which will produce around 2500 uV when excited by the same reference signal from that same record. Also, the output termination resistance needed by a MC cartridge is around 600 Ohms compared to 47,000 Ohms for a MM cartridge. A transformer will make that termination translation.
So, if a MC cartridge is your choice transducer for record reproduction, a transformer is often used between the cartridge output and the preamp input. This transformer performs two tasks. First, it elevates the Voltage from the MC to be compatible with the preamp requirements. It also provides the proper termination resistance conversion from 600 Ohms up to around 47,000 Ohms.
Craig
So, if a MC cartridge is your choice transducer for record reproduction, a transformer is often used between the cartridge output and the preamp input. This transformer performs two tasks. First, it elevates the Voltage from the MC to be compatible with the preamp requirements. It also provides the proper termination resistance conversion from 600 Ohms up to around 47,000 Ohms.
Craig