Advice on SUT for Koetsu Rosewood - EAR MC-4, Slagle/EMIA, other

My system is a Koetsu Rosewood Signature (.4mv), Jelco 850M on a Sota Star Sapphire, Berning all-tube bespoke capacitance coupled preamp (46 dB gain on the MM stage, Jensen transformers on the moving coil stage), Quicksilver v4 monos, Verity Audio Pafisals.

Jensens are some of the very best SUTs made anywhere at any price.

They are Jensen JT-347-AXT Step Up transformers (1:12 ratio configured). Given these and overall MC gain of only 64dB, does this explain my lack of dynamics with the Koetsu Rosewood Signature (.4mv)?

@montaldo
-And that is one of the best that Jensen makes.

Now there are some things you should know about when you use an SUT and this applies to all of them: SUTs need to be loaded correctly in order to perform correctly. Not to go into it with too much depth but transformers have an input side (primary) and output side (secondary). If they are not loaded at all, the inter-winding capacitance comes into play and the transformer will not have proper bandwidth- it will look like a flattened bell curve. If the transformer is loaded too heavily, the output will be rolled off!


The cartridge itself doesn’t need any load if an SUT is employed! IOW **never** attempt to load the cartridge if a Step Up Transformer is in use!! Instead, you load the output of the transformer, and the correct loading values change depending on which cartridge you are using.


Again, this applies to all SUTs. BTW cartridge loading is a different topic but in a nutshell for this conversation the impedance of the cartridge is what is requiring the loading of the SUT to change depending on the cartridge.


Now in the case of Jensen, they’ve sorted out what the correct loading values for most cartridges actually are (including the Rosewood Signature). If you contact them they can advise you on the proper loading the JT347. You’ll have to talk to David about how to install the loading in the preamp.


Seriously, the Jensen is excellent! But to unlock its performance you **have** to pay attention to proper loading, and this will be true no matter what transformer you use!!

Thank you Atmasphere!  the Berning preamp has loading plugs for the moving coil section but if I understand what you're saying correctly those are for the INPUT side whereas you think the Jensen transformers themselves may need  loading on the output side. Is that correct?
If so it sounds like I should contact Jensen and ask what kind of loading should be added to mate with the koetsu Rosewood signature.
Since the consensus is that the Jensen Transformers are excellent and the 8:1 winding is not a huge mismatch, this output loading is a hypothesis that might explain what I was hearing with the Hashimoto transformers. So maybe the Hashimoto simply  had a better loading match and weren't necessarily superior sounding. Maybe is a road to fixing this.

I use a 1:20 step up with my Koetsu RSP and it is a perfect match.  

I use the most revealing Lundahl silver SUT with my Platinum. That's the 1931AG IIRC. Not cheap - but they are almost as good as a noiseless gain stage.

Again my ignorance raises its head, but would the ideal windng ratio for the non-platinum be different?  I believe the impedances are the same but the output is .4mv for mine, not .3mv (platinum). I imagine the answer is yes as long as there would be "enough" overall gain?