which is better ? MC phono stage or MM+step-up ?

A great question and very dependent on a large number of variables, so difficult to say what is "better". I have tried various SUT's and head amps into my Aesthetix IO Sig, primarily to cut down on the tube rush at high gain (you remove some tubes for lower gain in this model).

SUT's generally add a level of dynamic, but can get brittle at the top end very much as Atmasphere describes. With a Koetsu, this can make it sound more alive, but I also agree there is a "ringing" effect that obscures detail. Having said that, in experimenting with loading my beautiful Verity Z, SUT beats, IO alone, Zyx pre pre and Accuphase C-17 and Pathos phono alone.

On my ZYX UNIverse, the ZYX pre beats IO alone, and best is the C-17. In general, my C-17 / IO gives better results, texture, soundstage, depth and believability, than any other combination. However ..... it took a lot of experimenting with IC's between head amp and phono before I got to that point and some cables made this combo the most ordinary sounding of all permutations.

So, I conclude, there is no specific recipe, just lots of trial and error to find the sound that suites your needs and I would argue strongly that there is no quantitative evidence that clearly indicates a preferential choice, notwithstanding personal preferences already noted in this thread by experienced audiophiles, with whom I would never argue with!

Steve

I recently heard some setups with the step up tranny and i like it better. It gives a more fuller, more dynamic sound.
Only issue is the hum-> it can get loud and audible.

Yes, SUTs are susceptible to hum. If running direct- there are big differences in high gain phono sections too, so comparison is anything but a level playing field!

This is were the the word "hobby" truly comes into play. I have a SS phono section with both mm and mc outputs. I always felt like the mm was much better than the mc side. So I started doing a lot of reading on SUTs. I obtained a set of transformers from a gentleman on Ebay and built my own.Wow, what a difference!
Yes you have to deal with hum, but there are ways to do that.
The sound is much more dynamic.The sound floor is lower and the frequency response is significantly wider,especially in the treble.The highs seems to have no ceiling.The bass is tighter and more defined.Everything is more coherent.
That said, the transformers I got were good quality Beyerdynamics with values that worked perfectly for my LOMC.

side bar: I emailed Bob of Bob's devices and he offered a lot of help,even though I am not a customer.I cannot say enough good things for a guy that sells a great product and yet is willing to help a DIY project.I would encourage anyone looking into a SUT to try one of Bob's.They start at a very reasonable price and are proven to be excellent.And of course his support is wonderful.

As for which is the way to go? There is no easy answer. I would say that if you are a plug and play guy that doesn't want to spend any time with tinkering with locating the SUT and trying different cables should go with a phono section. But if you are a analog hobbyist than SUTs are a lot more fun and interesting.In my book, a passive device will always have more POTENTIAL than a active one.But active devices are easier.Much like the passive preamp vs. active preamp.

One more thing.I have noticed that a lot of modern tube preamps with phono sections use jfets for the MC section.Many of the reviews of these preamps recieve high praise for everything except the MC jfet section.If you have one of these,a SUT allows for that nice tube phono section to be used instead of the jfet sound.

e

It is not the jfet. The Doshi Alaap uses a jfet mc gain stage most beautifully. Like others have said, the designer's experience and ability has a lot to do with it. I believe Nick has shown that a jfet solution can work extremely well. I'm sure there are others who can make it work also.