Step-up transformer designed specifically for high output moving coil cartridges rather than low output moving coil cartridges.  High output moving coil cartridges in the range of approximately 1mV to 2mV can often benefit from the addition of the MC1-H to raise the signal voltage by 10dB before feeding the signal into an MM phonostage.  The low turns ratio of the MC1-H (1:3) is ideal for this and improves the signal-to-noise ratio.

Further details here:  http://www.rothwellaudioproducts.co.uk/html/sut_for_homc.html