The cartridge mounted to the tonearm of your turntable uses a small stylus tip, made of diamond, to convert the information held within the groove of a record to a signal which can then be amplified for listening.
During playback the stylus tip, attached to a cantilever, is dragged through a records groove at a consistent speed, tracing the landscape of the record itself. The physical variations within the groove causes this assembly to vibrate, and it is this physical movement which can then be converted into an electrical signal through electromagnetic induction.
Electromagnetic induction is a phenomenon that occurs when an inductor is placed within a varying magnetic field. As this magnetic field changes, a current will be induced within the inductor proportional to the rate of change of the field. This principle is integral to the function of a cartridge and is achieved using magnets and coils of wire.
Moving Magnet Cartridges
A moving magnet cartridge uses magnets fixed to the end of the cantilever. These magnets sit within a static set of wire coils, moving within these coils as the stylus travels along the record groove.
This movement causes a variation in the magnetic field, inducing a small current within the coils that corresponds to the movement of the stylus. This current can then be amplified for listening using a phono preamplifier.
Moving Coil Cartridges
The principle remains the same for a moving coil cartridge, with the primary difference being that in this assembly the coils are mounted upon the cantilever, whilst the magnets remain fixed.
In this formation it is the coils that move in relation to the magnets, causing a variation in the magnetic field, and in turn inducing a small current. These coils of wire are often much smaller than those used in a moving magnet cartridge, and due to this the signal generated tends to be of a much lower level. Therefore, moving coil cartridges require a preamplifier with a dedicated MC input to provide the additional gain necessary for optimum performance.
As the coils are mounted directly to the cantilever of a moving coil cartridge, the cantilever assembly itself is much lighter in comparison to that of a moving magnet cartridge. This lightweight design contributes to an improved transient response, better clarity during quieter sections of audio, and more detailed reproduction overall. However, cartridges of this type are therefore much more delicate and tend not to have any user-replaceable parts as can be seen in many moving magnet cartridges.