Which SUT? .... for .3mv/10 ohms MC cartridge into 3mv MM input sensitivity

Long before I started representing Music First Audio and Audio Note I gave up on fully active amplification of the tiny signal from a MC cartridge. I have compared many, many preamps, phono preamps and step-ups. Most step-up transformers do indeed sound compressed. Most fully active MC phono preamps do indeed sound "electronic". But the best transformer step-ups into a MM phono stage have sounded much better, to me, in every way compared to the best active head-amps or MC capable phono preamps.

Now that I carry transformer step-ups from both Music First Audio and Audio Note (and MM-only phono preamps from both), it has been very easy for me to demonstrate this. I have a very nice MC-capable Krell preamp, that sounds better with any of these step-up transformers into its 47000-Ohm MM input. And, I encourage anyone who is interested to borrow one of my demo step-ups, to try in their own home, and find out for themselves.

The answer to your question, in my opinion, is yes. Listen to your MC cartridge, into the MM input with a good step-up transformer that is matched properly to the cartridge. If you tell me what cartridge you have, its output impedance (or coil resistance), and output mV, I can tell you what range of step-up ratio will work well for you.
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later he added

So the most versatile approach is to try a 1:20 transformer which has a provision for adding loading resistors, or is adjustable with built-in resistors. The next best solution is to compare more than one transformer, within a step-up ratio range between 1:30 and 1:20.