SUT - electrical theory and practical experience

SUTs are about gain. You can increase gain via a transformer or a circuit. As with most things audio some methods sound better and have other advantages than others 

All these things can be covered by a good phono pre-amp with adjustments for such things.

I can only talk a little to the practice. An excellent SUT represents a real improvement over most transformers present in phono stages. 

Which is to say a good SUT is preferable to a mediocre SUT, on the assumption that built in SUTs are mediocre. But what about Allnic and a few others with very high quality built in SUTs? The advantages there include fewer connectors and ICs.

I can only speak a little to the theory.  A step up transformer works on the same principle of voltage transformation used for AC power products.  For instance, when you buy gear designed for US voltages but want to use it in Japan.  Transformers can convert one voltage to another, but the power on either side of the transformer is roughly the same (minus losses). 

That is, a 100V to 120V transformer will still have the same power (current x voltage) on either side, 

That is also how I generally thing of them as well @erik_squires - but they are also a current converter to some extent… and the current coming in gets changed inversely proportional to the voltage change.

And… also they (SUTs) work on magnetic fields so they are a current device.

@drbond Maybe think of a 10:1 transformer as increasing the winding on the cartridge by 10x?
Just not making the cartridge’s motor 10x heavier.

I am still a bit uneasy as the cartridge is more of a current generating motor than a voltage generator.

Pretty sure one cannot be a fan of Sutherland, and other trans impedance phono stages… and simultaneously a fan SUTs. Maybe it is possible.