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

I like to add as little gain as possible. My phono/pre has a LOT of headroom, right on the edge of using no boost at all (accomplished with multiple devices in parallel). For many records, that is sufficient. For some, the Lundahl is useful, and easily the best I’ve tried (includes Koetsu’s own, Hashimoto, and Sowter; but not Jensen).

The 1931AG adds the least gain. That would be my suggestion for a KRS. The fine fellows at K&K Audio (no affiliation, just a satisfied customer) are very good guides - talk to them about your system. So is Mr. Lundahl, a gentleman of the first water.

If you can’t afford the silver, I’ll bet the 1931 with copper windings would be better than anything else you could buy - but remember, SUT’s don’t wear out. You only buy them once.

Please read Ralph's comments with attention - that's atmasphere.

montaldo,
You can try contacting Isao Asakua of Hashimoto, he can help you in getting the right transformers for your application. Isao Asakura, support@obsinc.us. I was going to go with Hashimoto SUT’s myself until I found a pair of MU Audio SUTs, they have Stevens and Billington transformers inside. The Hashimoto are excellent, definatly superior to the Jensen’s, and the MU audio are better still. If you have to add loading its going to drop your gain and degrade the sound. Better to avoid that if possible. If you have a good tech, he can install the Hashimoto’s in your phono pre if there is space and you are good to go.

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?

I can't speak to the Berning as I'm not familiar with its innards but to the last question, any and all SUTs should be loaded on the output side and the cartridge should never be loaded at all since the SUT is doing all the loading via its ability to transform impedance. So when its loaded correctly (with the cartridge at its input) there is simply no need to load the cartridge.

As an additional note, cartridge loading is for the benefit of the preamp not the cartridge. If the preamp has good RFI immunity no cartridge loading will be needed. When the SUT is used, it blocks RFI generated by the cartridge inductance and tonearm cable capacitance, so no need for cartridge loading. Clear as mud? 


An additional note: the amount of gain you ask of a transformer also degrades its performance. So the least amount of gain you get from it will always be the best. Also, if you use a different turns ratio the correct loading will change.


Until you are able to sort out this loading issue, its quite pointless to compare transformers!!! Some transformers are designed to be fairly well loaded when presented with a 47K load and a nominal cartridge resistance, others are not (IMO Jensens fall into the latter category; they assume that you are going to pay attention and get the loading right). In a nutshell you would then be comparing apples to oranges. Any SUT comparison needs to have the SUTs on an even playing field; both need to be properly loading which will not be the same values! The transformer manufacturer should **always** be able to to supply you with the correct loading values (which will usually be a combination of a resistor and capacitor).

Ralph, you would think the transformers would be designed for a 47K load which is pretty standard for MM phono stages. If not 47K how would you figure out what it was? Just a meter? Also why the capacitor. Wouldn't just a resistor do? I know you might have to change capacitive
loading for a MM cartridge but why the transformer?

Mike