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

Mike the the formation so far has been confusing at best.  You might be best served talking again to Dave at intact and call Kevin at K+K audio.  The ratio of the step up is squared then divided into the 47,000 resistor.  So 10 to 1 is 10x10=100 then 47,000÷100=470.  So the cart is seeing a 470 ohm load.  There are ways to parallel resistors to lower that value but not increase it.  The cap is use if you want a zobel network.  Some guys like others do not.  

If you really want total control with step up ratios and cart loading you need have your friend bypass the 47,000 and play with various resistors externally.  Then when have what you want you could replace the 47k with the new value.  If you sell the phono stage latter you could put back the 47k.

Without total control of the step up and loading you never really know what your cart is capable of.  And of course the transformers also have a sound of their own. 

Maybe Dave or Kevin will build you a sut box that you can plug in different resistors and easily change step up ratios.  Then bypass the 47k in the phono stage and you are good to go.

Enjoy the ride
Tom

 After after all our exchanges, which I appreciate so much, I decided an experiment might be useful. So I am buying a used Intact Audio 1:20 copper SUT to just try and see how different it sounds from my internal 1:8-ish Jensens in my Berning pre. I will report back this weekend.
Stu

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?

@mijostyn They are designed for 47K, but any transformer designer worth his salt knows that the transformer isn't going to work perfectly with that- and that it will also change depending on what cartridge is used. IOW they know that it has to be loaded correctly (if they don't, they are leaving performance on the table). The capacitance has to do with the fact that you will likely get a peak somewhere that might not show up from simple ringing of the transformer with a square wave.


@montaldo If you don't get the transformer loaded correctly, you will hear differences but they won't tell you anything about which transformer is better! On top of that 20:1 is very different from 8:1.


To get to the right loading values for the transformer you have to talk to the manufacturer of the transformer. The only way I know to do this empirically on the bench is to  apply a square wave in series with the cartridge and look at the output of the transformer on an oscilloscope and vary its load to get a very slight amount of overshoot.


The problem here is that the capacitance of the tone arm interconnect cable is a variable, as well as the capacitance of the cable at the output of the square wave generator, and you run the risk of damaging the cartridge by deguassing it.


This is why I like working with Jensen, as they have demonstrated over and over again that they know and care what they are doing. Most SUT manufacturers can't tell you how the unit works with every cartridge out there.

Ralph, Sowter offers different step up ratios and tells you what cartridge impedance range the transformers were designed for. Is that enough in and of itself to get you headed in the right direction? I have installed them in the past and as far as my ears can tell they worked fine.

Ralph, I will ask Dave Slagle what he thinks about my setup and loading. The original sound tradition Hashimoto hm-7 I tried had an even higher winding ratio such as 1:30 I think. It sounded pretty amazing with 29dB gain. But it was a little too big and "in my face." This will be 26 dB on top of 46 dB of my linestage, which seems reasonable.

As fas the loading issues I still don't understand all those variables so I will continue to listen to you guys and talk to Dave Slagle as well.