Step-up Transformer, what's lost?

Herron phono amp has two versions one for MM and one for MC. The MC version has about 66db gain that should be enough for the Dynavector unless your preamp is very low gain also. Are you using the MC version?

Okay, look, we have 2 situations here. Standard MM input with a gain level for about 4mv cartridges, and some type of MC input with higher gain for a low-output MC cart. There is no free ride. Either you have a step up transformer into the MM stage, or you have extra gain stages in the MC section. Pick your poison. The additional gain stages in the MC section are at least as objectionable to signal quality as a step up transformer. Personally I use a step up transformer because I think it is less problematic than additional gain stages. Others think differently. If you have a decent step up transformer, or a decent MC stage, you should not be corrupting the signal in a real bad way. My Cotter transformer passes a nice clean step up, that sounds real good to me into my MM stage.

And you can't get around the issue with a MM cart or a high output MC, because they have heavier moving structures than a low output MC and so you have a very likely possiblility of losing something there.

If you are looking for what the "experts" say, Kondo, the total "audio guru" who makes some of the most musical gear in the world, specifies only a transformer is to be used to step up his top of the line cartridge. A step up transformer does not have such a limitation like an amplifier output transformer, because very low level signals are being used and saturation is really not an issue. And if you don't use a step up transformer, and your MC stage has insufficient gain, then you raise the noise floor by turning up the volume, and obscure low-level detail that way. You have to use one method or the other to use a low-output MC. You have to choose one. I chose a good quality step up transformer, and I am happy with it. I would dare say that if you heard my system playing, you wouldn't be talking about any lost detail.

a good step-up costs pretty-much the same as a good phono $1k or higher. there could be a-bunch of different contraversal issues in this case since high-gain mc sections tend to have more than one amplification stages and/or a step-up transformer as well. also all-tube phono preamps either very costly or have not enough gain to handle super-low output cartridges.
cary audio came up with inexpencive solution and i'm sure that there are more brands that have electronic approach for a step-up that for the money is more efficient than step-up transformer.
in general for this issue i tend to partially agree with Blptwp for the MC cartridges not higher than 2mV on the output used with phono-sections 50...55dB since the coil length does affect pretty-much as amplification stages or step-up transformers.
for herron phono preamp you can use as low as 0.5mV output cartridges and mainly you need to step-up another just 6...8dB. if you go for step-up passive device you should probably research Quicksilver or EAR step-up transformers that will minimize any losses and boost the volume. Also less expencive Ortofon T1000 can just do that job. In high quality transformers you can select the gain or even use the unity gain just to match impedance with no headache. If minimal gain is used on the high quality step-up device you should hear no difference in terms of details.

G_m_c and Sidssp are right. 65 db gain in your phono should have enough gain for your cartridge.

Consttraveler,
I believe you won't be satisfied with step-ups. However, many audiophile use them with satisfaction. I guess it all depends on your expectations. I was not satisfied with step-ups because I knew what the sound quality was supposed to be like without step-ups even though without dynamics. The sound did changed for sure. I never liked SS step-ups. I had tried 4, including the one made by Benz Micro. Tubed step-ups are very difficult to perfect because of different tubes have different sonic characters, trying to get the sound you want to match tubed step-up and your tubed preamp and phono section means endless tube rolling. I did all that and through with it.
Your choices are, if you don't want to change cartridge, to try different step-ups. Based on 0.23mV output, your phono must already be a high gain phono. Be very careful when you add a step up. Too much gain will really be a bad thing, I have tried that, it sounded aweful. Or, get a phono stage with even high gain. If your phono stage is already high gain, do not use a step-up period.