Can I use a step up transformer?

Of course there are pros and cons to both sides of the argument.
I was happy with the inbuilt phono-stage of the Halcro DM10 (which was compared favourably to the Boulder 2008 in Stereophile) and never contemplated an SUT until I had the opportunity to hear the Kondo KSL-SFz in my home system with a variety of cartridges.
Now there was not an overwhelming difference in the overall presentation of the two methodologies (in my case at least) that anyone could say was immediately apparent and it took a great many listens to a variety of music for me to become convinced that the Kondo offered just a smidgeon more transparency on most cartridges.
On the Sony XL-55 (0.2mV) there was the slightest hum audible (only between tracks) and thus I prefer to run that through the active Halcro MC stage.
The Kondo is one of the priciest SUTs available, totally wired with silver and with silver RCA interconnects so perhaps a lesser SUT might not outperform the active Halcro phono- stage?
As with most things in this hobby of ours.....it's hardly advisable to proclaim the superiority of a single universal direction.
You pays your money and makes your choices 😎🎼

One advantage of using an SUT (which I've never seen mentioned) is the ability to now alter the loading just as one can do with a MM cartridge.
Because the SUT plugs into the MM input of the phonostage, I can dial in a Resistance anywhere from 10K Ohms to 60K Ohms and the cartridge responds in the same way that a MM does.
Now I don't understand the science behind this and hope that others here can explain what is actually happening......but it works a treat on taming an aggressively bright LOMC and conversely, one which may sound slightly recessed or shy?

But Master....it sounds so much better with the SUT.

Grasshopper.....it only sounds better because of the colossal distortions.
You need to eliminate all better-sounding equipment and insert ’finer’ pieces elsewhere in your system.

But Master....how will I know I have reached Nirvana?

You will know Grasshopper, when you have inserted enough ’fine’ equipment to give the foulest of sounds.

And then Master, will I have eliminated these ’distortions’ of which you speak...?

Only then Grasshopper......only then...👼🏼