Can I use a step up transformer?

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?

Dear @halcro : Please read very carefully here:

https://forum.audiogon.com/discussions/can-i-use-a-step-up-transformer/post?postid=1342503#1342503

because those changes in quality performance level comes from the very complex interaction that produce impedance/inductance internally in the phono stage that can’t handle with aplomb it, not comes from the cartridge that is non-sensitive to those load impedance changes. Problem is in the phono stage that comes with some kind of " faults " by design.
Obviously that in an active high gain PS this kind of design is not for use with external SUTs so it’s not a design faulty, the designer made it to use it in the active high gain and not the other way around . The designer in your unit never imagine that some one will use the MM stage along a SUT, so there is a " problem " in that MM stage. 

The designer of your unit knows very well what I'm explained in this thread and that's why he left in the active MC high gain stage  a fixed 220 ohms impedance that you can't change it because is not need it to do it.

Please read it.

Regards and enjoy the music,
R.

If phonostage gain not enough, investing to higher output cartridge is wiser than to SUT. That's where math easily replaces all the science behind.

Dear @czarivey : Agree with.

If for example an active gain PS was designed for cartridges over 0.3mv and has no MM stage and we want to listen a 0.20 mv cartridge then we need to change, either, the PS or the cartridge with  higher output level.

As I posted, with LOMC cartridges what we always need is to match Phono Stage gain not impedances.

I think that existed and exist a misunderstood ( including me. ) not only on SUTs but in the overall subject.
Many vintage SUTs and even today ones comes with the possibility to choose different " load impedance " ( normally a selector switch: 3 ohms and 40 ohms or 20 ohms or whatever. ) and where the selected " impedance " has different  gain( 34 db, 26 db or 20 db or whatever. ). Other SUTs only said:  3 ohms to 20 ohms.

ALL those created the misunderstood because in a SUT we don't have to match the cartridge impedance with the SUT impedance that as a fact does not exist as we could think.
Again, only match gain with the phono stage.

Phono stages that comes with a selctor switch for MC load impedance ( normally at th first input stage. ) or/and different  gain levels goes against the quality performance level of the cartridge signal: it performs a signal degradation.

Overall interaction of all  these and the PS design generates several anomalies/distortions even could affect the critical/delicate equilibrium in the passive RIAA eq. frequency response deviation on both channels and certainly we can hear it.

@thuchan posted:   """  Good systems deserve using SUTs!  """

i disagree with. What we need for LOMC cartridge is way better active high gain Phonolinepreamp designs and that's all. I think this is still the real challenge for all designers.

Regards and enjoy the music,
R.