Step-up transformers for moving coil cartridges are the most esoteric and
misunderstood items in the world of hi-fi.
And this partly explains why they are so seldom used. This is a great shame because the use of a good transformer gives the best possible performance from a moving coil cartridge.
The big advantage of moving coils is that the coils are much lighter than the magnets, so they are much more responsive to the motion of the stylus. The big disadvantage is that the output voltage of moving coil cartridges is about 20dB lower than that of moving magnets, so an extra 20dB of gain is required. The extra gain can be provided by the phonostage amplifier, by an external device called a headamp, or by a transformer. The most commonly found solution is to increase the gain in the phonostage, but step-up transformers are still the best solution where cost is no object.
Apart from the issue of noise, the sound quality of transformers is something we -as their advocates- swear by. The distortion produced by audio transformers is of a completely different nature to that produced by a transistor amplifier. The harmonic distortion in transformers is greatest at the lowest frequencies and falls rapidly as the frequency rises, whereas in transistor amplifiers distortion more usually rises as the frequency rises. More importantly, intermodulation distortion tends to be lower in transformers than it is transistor amplifiers. The outcome is that although transformers aren't absolutely free of distortion (nothing is), the distortion is very benign compared to the distortion produced by many transistor amplifiers. This explains why the sound produced when a moving coil cartridge is used with a good transformer is so sublime and can create an open and spacious soundstage with amazing separation between instruments.
Audio Note offers an extensive range of step-up transformers, each with different 'loading' options to make possible the best results with (our) moving coil cartridges. The (impedance) matching of the transformer with the cartridge (and phono-preamplifier) is for many a complex subject, and its best to ask us to suggest the optimum solution as you will find much ill-informed advice on the internet.
All Audio Note MC transformers are housed in solid copper chassis’s for best sound. Despite this they are quite sensitive to positioning, and hum will occur when they are too close to power cords, supplies or electric motors and their associated wiring (from a separate turntable power supply to the turntable itself for example), so careful positioning is mandatory.