SUT - electrical theory and practical experience

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.

Holmz, please read my long post and Larry’s too, near the top of this thread. Of course transformers transform both voltage and current in direct proportion. The product of volts X current on the primary equals the product of volts X current on the secondaries. Don’t make the subject harder or more vague than it needs to be.

Dave Slagle is well a known and respected manufacture of custom SUTs and does an excellent description of the theory and details - intact audio.  Beyond that he winds with both copper and silver, and each will have a different perspective to the music.  There are variations in core material that can influence the sound with each SUT manufacturer often favoring one over another.  

My own experience has been quite positive moving from a solid-state phono-preamp to a Tron Seven Reference with SUT and tubes and was quite surprised on the overall improvement, much more than incremental - equally quiet with better bass and overall extension and soundstage.  But the devil is in the details, and results can vary.