I'm new to Step Up Transformers

Most SUTs, the gain and impedance load are inter-related, some SUTs have optional but not separate settings, like my Fidelity Research FRT-4, but the 4 optional choices are still inter-related, i.e. more gain = lower load. (Load = typical 47,000 ohm phono input divided by the chosen x factor squared), 

SUTs or Phono Stages with separate gain and separage load settings are needed for some cartridges, as the standard ratios don’t fit properly.

Soundsmith says Paua output 0.4mv signal strength, it’s coil is 10 ohm resistance, (very much like my AT33PTGII 0.3mv/10 ohm coil). The strange to me part is they advise a load of greater than 470 ohms?????

industry guidance for MC impedance load says try coil impedance x 10, i.e. try 100 ohms. anybody know why they advise 470 ohms for their 10 ohm coil?

GAIN: they advise a TOTAL gain of 58-64db, keep in mind, that is total, including whatever your MM phono is doing AFTER you pre-boost with a SUT.

i.e. my SUT boosts my AT33PTG 0.3mv x 20.68 x factor (+26db) thus up to 6.20 mv that I then send into my MM Phono input for RIAA EQ and it’s gain. Luckily it does not over-load the MX110z’s phono stage, not sure what it’s limits are.

My SUT has a 10.55x gain option, (+20db), the load is 423 ohms, closest to Soundsmith’s stated 470 ohms.

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btw, My experience: my SUT does NOT have a sound characteristic of it’s own, it is dead silent, simply and passively boost a too weak signal, allows me to use my existing preferred MX110z Tube MM Phono Stage

is this version yours?

or this earlier version?

In either case, you would use the MC input, and mess with your load options, try 100, try 500, hear any differences, preference, you cannot hurt anything

An MI cartridge with a 10 ohm internal resistance like the Paua and some other soundsmith MIs is not comparable to an LOMC with the same internal R, because LOMI cartridges have a MUCH higher inductance, at least 100X to 1000X higher than the LOMC. The inductance adds to the resistance as frequently goes up. Thus the recommendation for a 470 ohm load as a minimum. Dave Slagle mentioned yet another reason for the recommendation. I run MI cartridges with a 1k ohm load, minimum, usually 47K ohms.

The Zestos model I have is the PS-1 (bottom photo).  I did experiment when I got the cart (2 weeks ago) and found 1000 ohms to be too bright and thin. 

   I believe I ended up at 800 ohms (at least for now) and that setting gave a nice airy high end without it getting thin. 

    Lower settings started getting too dark or dull.  But I am told that carts have a break in period so all that could change.

FWIW, my favorite cartridge is a SoundSmith Hyperion, my SUTs are 10:1, but I also fearlessly interchange a variety of LOMC from Ortofon, AT (the recently introduced AT20 is quite nice), and others.  My philosophy is to try things and listen.  BTW, listen means for a while, not just for a minute or two, maybe at least an hour or more after making a change.  I like to give my ears and mind a chance to adjust to the sound of what I am trying.