Koetsu Urushi + MC step up transformer

I agree with Nsgarch, but meantime you do have those Lundahls and maybe fooling around with the load resistors will help make them sound better. You say you "tried some different" values, but you don't say what values exactly. As others have said, the Urushi likes to see ~100 ohms load optimally but will probably work as well into slightly higher load Rs. Do you know the turns ratio of your Lundahl trafos? A trafo reflects an impedance that is related to the square of its turns ratio. If the turns ratio is 10:1, the square of that is 100 and therefore you want to place a 10K ohm resistor (100 X 100R, the preferred load for the Urushi) on the secondary side of the trafo that is driven by the Urushi on its primary. You don't say what values you've tried or whether you had professional help in selecting the values, but maybe this bit of info will help. If the CJ has fixed 47k ohm Rs in its phono input, you will need to calculate the value of R that will give you a net of 10K ohms, when placed in parallel with 47K ohms. Then solder those resistors in parallel with the 47K ones and you are done (or just remove the 47K resistors and substitute 10K ones). In addition to this simplistic approach, performance of the trafo can also be improved by a Zobel network, the design of which is much more complex. See the Jensen transformer company website for ideas on that or ask K&K.

Nsgarch, You wrote, "spider, the values one uses to match a MC cart to a SUT have nothing to do with the load resistance you would use if connecting the cartridge to a phono preamp or headamp." Are you suggesting that my advice in my previous post was completely incorrect? If so, I'd like to know, because I hate to think I've misinformed spider (or anyone else). When he bought the Lundahls (presumably from K&K), I presume that they knew how he was going to use them and that therefore the ones he's got are already a reasonable match gain-wise for the Urushi playing into the CJ.

Re your last post, the consensus among us other users of the Urushi is that you would be best off with a load of ~100ohms. If you really want 47K ohms, then just off the top of my pointy head you will need to replace the 47K resistor at the input of the CJ with a very much larger one; the value would be 169 X 47K (given your reported 13:1 turns ratio), nearly 10 Megohms! You may as well try 10M. I don't recommend it but try it if you are convinced that the cartridge performed best into 47K ohms load. You are not alone in this belief; Allen Wright, a well-respected designer and manufacturer runs all his LOMCs into 47K. You need either to remove the stock 47K load resistor entirely and replace it with 10M or to place 10M in series with the 47K one.

I just did not want to be the dispenser of incorrect information. I've never used a SUT either, but I came close at one point and read some of the excellent white papers on the Jensen website at that time, to gain what little knowledge I have on the subject.

Spider, I hope it's clear in all this that the circuit should be as follows: cartridge to transformer to load resistor, so that the load resistance is on the other side of the transformer with respect to the cartridge and replaces the built-in load resistor in the preamp. To really make it simple, you could just leave the 47K resistor in place. With your transformers, that would result in a very acceptable load on the Urushi of about 200 ohms. (I'm too lazy to do the math.)

Subbing the 47K load resistor with an 8M load resistor would only negatively affect the phono stage if the input tube or transistor cannot tolerate it. I'm not sure how it would work with a transistor input, but with a single-ended (as opposed to "balanced") tube preamp, the "load resistor" is actually the grid resistor as far as the input tube is concerned. (Actually, this is true for full balanced input as well, but it's a bit more of a complex topology.) The question would be whether that tube can tolerate such a high grid resistor. The typical tubes used for input in a tube phono stage (12AX7, 6922, etc) can tolerate a 1M resistor with no problem, depending upon the bias voltage. To determine whether an 8M resistor is problematic, one would have to consult a manual for the specs of the tube in question, and it would be prudent to know the bias voltge. But most likely - no problemo. As for the rest of the circuit, the value of that grid or load resistor would have no effect on RIAA equalization and should not effect the sonics except in that it affects the cartridge output, which is what we've been talking about. The only other thing that occurred to me was whether the behavior of the transformer will be unaffected when there's an 8M resistor (i.e., a very tiny load, almost no load) in it's secondary. But I think you're doing the right thing by leaving the 47K R in place, so the Urushi sees 278 ohms. You may be quite happy with that.

You're rationale for selecting the next highest load R below 47K sounds reasonable but tedious.

On the Jensen website you will find a white paper on use of Zobel networks with their transformers (which are excellent by the way). I don't see why the info is not also applicable to any other SUT, but it may be so if the design of the Zobel is based on the frequency response of their trafos in particular.

Have you yet tried connecting the trafo to the input with the standard 47K-ohm resistor in place, in other words with no other changes? Should at least work well. The networks etc are for touching up the response to make it as flat as possible; a Zobel or added capacitance is certainly not a requirement.

Can you be a little more descriptive? In what way does it "suck"? Do you lack gain even with the SUT? Is it bass heavy or exaggerated in the treble? Is it grossly distorted? Are both channels behaving in identical fashion? Etc...

Since I believe K&K are the importers of Lundahl, you may be able to get good advice from Kevin. He is very knowledgable.