Raul, in your links, I don't see much that I would ackowledge as being "facts."
To address your comments one by one, yes, distortions will be generated at the core of an SUT, but distortions are also being generated in any MM or MC cartridge (both in the signal core and in other places). In your recent posts you have noted a preference for cartridges that measure to be poorer than normal in terms of distortion. If you clearly can like cartridges that measure to have higher-than-normal levels of distortion, why are you afraid of distortion in the SUT?
Bandwidth of an SUT may not go down to DC, but I have a test transformer on my bench that measures dead-flat down to 10Hz, with a -3dB roll-off of 1Hz. The top end is dead-flat to at least 30kHz (the top-end response after that depends on the load). Far better than any loudspeaker, for sure.
True, an SUT has a reactive electrical component, but so does any cartridge that has an inductive output (all of them) when you use it with an interconnect cable that has capacitance (again all of them). The audibility of the resulting electrical resonance is directly related to the inductance of the cartridge (high inductance plus cable capacitance means a resonance that may be close to the audible band and can be measured and heard directly, while low inductance means a resonance that remains at RF frequencies, and shouldn't be directly audible unless your phono stage has linearity problems at RF frequencies and IMD subsequently allows the electrical resonance to fold down into the audible band). At least with a stepup transformer, you can physically place it close to the phono stage and keep the interconnect cables ultra-short (thereby reducing capacitances). With a high-inductance cartridge like an MM, you need to keep the cable long (therefore meaning high capacitance), and this will give you an electrical resonance that is far more likely to be directly audible and also measureable in the audible band. This is why, although high-inductance cartridges like MMs make life easy for many phono stages due to the high signal voltage, many audiophiles still prefer low-inductance MCs, even if they need to use stepup transformers into low-gain phono stages. FWIW, every MM that I've listened to and thought sounded acceptable had low inductance.
Mind you, normally and by preference, I also prefer to design with and use fully active amplification when it comes to phono equalizers. However, I know from first-hand experience that it is possible to design a stepup transformer that at least measures pretty well and sounds reasonable. And let us not forget that there are many phono equalizers that audiophiles like and already own that would benefit substantially from some extra gain with small noise penalty (and also in some cases, benefit from judicious band-pass filtering). Both of these are attributes that a stepup transformer can easily provide. Let's not insist that audiophiles throw out their existing phono amplifiers just to satisfy a technical argument which doesn't appear to be on such solid foundations.
regards, jonathan carr
