I'm new to Step Up Transformers

My Zestos does have a MC section - it has settings for Low Gain or High Gain. 

My confusion was because a friend with the same phono preamp as mine was telling me a SUT would improve the sound. And others online were saying similar things. 

Your Zesto Andros already has SUTs for MC application internally, followed by an internal tube MM phono section. They are Jensen's as used by Lamm, Conrad Johnson, ARC and others.

You would only benefit from using an external SUT if it was higher quality or suits better your cartridge than the internal SUT's in the Zesto. Having installed a Zesto with a variety of top MC's it is a very flexible SUT with multiple loading options. You would have to spend large to get a significant improvement.

@rmcfee

I am quite familiar with both the Zesto and the Paua.

The Paua needs to see a load of at least 470ohms.

I fiound with my sample the optimum load at 1000 ohms.

I would strongly suggest you try on the moving coil input on the Zesto both the high and low MC input settings and both the 400 ohm and 1000ohm settings to find the best combination.

If you try an external SUT you must ensure that the SUT has a maximum turns ratio of 1:10 to be sure the Paua is loaded at a minimum of 470 ohms.

The Zestos model I have is the PS-1 (bottom photo).  

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. 

If you have an 800 ohm loading option on the back panel then you probably have the upgraded version Zestro Andros 1.2

My mistake - I definitely have the PS-1.  The setting I settled on was 200 ohm I believe.   

That's way too low. I would suggest trying at least 400 and check your set up - recheck your VTA, tracking weight etc . The Paua is a very smooth sound, slightly warmer than the more expensive soundsmith's due to the aluminium cantilever. It should not be sounding bright and thin at either 400 or 1000.

Have you tried the two gain settings on the MC input ?

But if you read the pdf available at Jensen, you see they recommend a rather complex network of R and C to get correct loading. Almost no one actually does that

You are talking about a Nobel network to dampen any ringing in the transformer.

The Zesto Andros has the Nobel network included in their circuit, along with loading options designed specifically for that transformer/zobel. I know this because I installed an in field factory upgrade on a Zesto Andros a few years ago.

The slight complication here is that the Paua is a moving iron not a moving coil so the behaviour will not be at the same as LOMC's.

Soundsmith can advise on which transformers are appropriate.

I am constantly surprised when others report they hear important differences between two different load resistances, using LOMC or LOMI cartridges, that are numerically very close to each other on a scale of 100 to 47K ohms. Like 725 vs 525 ohms or 800 vs 1000 ohms.

You make too many assumptions.

I agree on the MC that if small changes are audible, as Atmasphere has pointed out, it is more likely that the target phono is reacting.

However it is a different electrical model with a MI such as the Soundsmith.

I ran the Paua through 4 phonos in one afternoon, including the Soundsmith phono, and 3 others, both transformer based inputs and solid state and small changes in loading 700-800-900-1000 ohms were quite audible in all 4 phonos. If I recall correctly all 4 phonos sounded best with the same loading, in my case 800 ohms.

Paua owners please be aware that the Paua has undergone electrical changes through its lifetime, the inductance and other design parameters have changed over time so it pays to experiment - or follow the guidelines by Soundsmith.

The Paua is a moving iron cartridge and will work best with a high-gain phono stage - not an SUT.

This is not true.

Whilst I am not a fan of SUTs, it comes down to the quality of the various options and more importantly whether the high gain phono vs SUT-MM phono can provide the optimum gain and LOAD.

Each of the options has its plusses and minuses.

A Zobel network is often used to damp a transformer. But if you change the source impedance, the Zobel network won't be correct.

If you really want it right so the transformer editorializes least, the only way to really know is the procedure at the link I posted earlier.

Actually the best way is to put your cartridge/transformer on a scope and adjust the zobel to minimise ringing. This I would assume is beyond many here.

I actually used the Zesto/Zobel removed from the phono as a test bed - adjusting the zobel for a 40ohm Denon 103D (New) made very little difference to the sound, virtually inaudible, whereas changing the loading was more audible with that transformer ( Jensen ).

@billstevenson 

Which SUT are you using with the Hyperion ?

Have you compared many ??

Thanks.