My question is where do I go from here? Bob's makes the sky 30 which is switchable from 1:15 to 1:30 which I like because I can play with the gain tubes in my preamp and potentially go to a quieter 12au7 than the 12ax7 that's currently in there. Will that be a real improvement?
@rmdmoore We've worked with SUTs a lot over the last 40 years. @lewm's suggestion of Jensen Transformers is an excellent one- they make some of the very best in the business at any price.
One thing you learn very quickly is that you want the least amount of step up possible so as to work with your cartridge. The more step up you go for, the more issues the transformer can introduce.
If you have 0.2mV you really only need 60-65 dB of gain if you have a regular line section in your preamp. So you should be using the MM input, not the LOMC input.
The other thing that is tricky about SUTs is loading. The loading does not affect the cartridge (other than measurably and audibly limiting its high frequency bandwidth; lewm already linked to the thread on the Steve Hoffman forum that shows what is really going on), but loading is critical for any SUT!
If the SUT is improperly loaded it will either 'ring' (distort, so adding brightness) or be rolled off if loaded too heavily. Jensen transformers has published a pdf file that shows the correct loading for their transformers when used with most known LOMC cartridges. Mot SUTs made for a specific cartridge are designed to be loaded at 47KOhms with 100pf of capacitive loading (which is about the capacitance of the tonearm cable 1 meter long); IOW they are designed to be plug and play.
But if you use a different cartridge with such an SUT the loading will be off and it won't sound right! That is one reason I like to work with Jensen since they did their homework, figured out the loading values and so their transformers work with almost any cartridge.