Choosing an SUT?


I'm shopping for an SUT, how do I choose one.  My cartridge is a Soundsmith Zephyr MIMC ES star lomc cartridge.

Compliance  10um/Mn
Voltage          0.4 mv

Any suggestions? 
zardozmike
I have not found the low impedance MI carts to be a good match with SUT's.  While the reflected resistive load can be kept in line with what peter suggests, any capacitive load also quickly comes into play and causes a LC resonance with the cartridge inductance that quickly encroaches on the top end of the audio band.

the link below has a spice simulation of a 10Ω 2.75mHy MI cart into a 1:10 loaded with 47K.  The plots show 100pf, 200pf and 300pf of capacitive load.  

http://www.intactaudio.com/forum/files/screen_shot_2020_07_09_at_61836_pm_458.png

dave
I am considering trying an SUT for my SoundSmith MIMC Star into my Herron VTPH-2A. Sounds like arguments for and against this set up. Think this will work?
I am considering trying an SUT for my SoundSmith MIMC Star into my Herron VTPH-2A. Sounds like arguments for and against this set up. Think this will work?
I got a SUT from these guys:  http://www.sacthailand.com/transformer_mc.html   They were recommended to me by someone with a lot of experience with SUT.  For a small additional charge, they will do a custom winding to match your cartridge if that is needed.  I am happy with mine but it the only one I have ever had in my system so can't compare it to anything else.  They speak English and were very easy to deal with.
I too found the Bob’s Devices Sky SUT preferable to the Herron’s JFET stage (though it is a very good JFET stage). As others mentioned, there are loads of SUT options, each with their own sonic profile. The Bob’s Devices are rich, robust, and fleshy sounding - on the warm side of things. They work well with a wide variety of cartridges.

HOWEVER, the thing about SUTs is that it can be tricky to balance optimal gain vs. optimal load if you’ve got one of those cartridges that asks for a relatively high ohm # for loading versus its output. This is somewhat the case with your Zephyr. Asking for more than 470 ohms load (others have mentioned it may benefit from a higher #) from a 0.4mV output is tough. You’re either going to be on the low side of optimal for gain or for ohms. Some folks are OK with less than 4 - 5 mV coming off of the MC step-up stage but I don’t like it.

One way to combat this is to find a phono stage that allows for flexible loading above 47K ohms in MM mode. Unfortunately this is more rare than it should be. I know the Rogue Ares allows for this (47K, 100K, or even 1 Mega-Ohm MM loading!) and so it can be a good partner with SUT for the usual "tough for SUT" crowd like the Benz non-magnetic ruby plate cartridges and (apparently) your SoundSmith. The Ares MM stage will be a slight step down from the Herron, but might be comparable to your Chinook. Then again swapping phono stage is a lot of effort just to try out a SUT!

One more consideration for SUT is that you will need a very short run of shielded low-capacitance RCA cables coming OUT of the SUT. If you want to hear cables make a huge difference IN A BAD WAY, then swap in some large gauge fire-hose braided geometry interconnects more than 1m long. Also you might have to deal with ground loop hum gremlins. The things we do for love (of analog)!