Cartridge incompatibility, Soundsmith and Luxman

That's for sure. If he wants to let the tail (the 100 ohm resistors) wag the dog, then he must acquire a LOMC with typical LOMC inductance.  But also gain must be high enough to work well with the inherent gain of the MC section (plus the linestage gain) of that Luxman. (I don't know what that is in db but evidently it was not a problem with the 0.3mV output of the Zephyr.)

Any good technician should be able to unsolder the old resistor and install the new resistor for under 100 bucks easily. I don't get where the OP thinks it's a 1000 dollar mod, sounds like someone was blowing smoke up his arse.

BillWojo

@billwojo where do you get $1000 from?! By the time I sell the cartridge I have and get a different one, it’s pretty much a wash.

I think am guessing that the $1,000 comes from the amount you are willing to spend on a SUT, such that paying for a modification would have to be at or above that amount to be out of the running as an alternative.  Most repair places will charge for the modification by the hour, with one hour at a minimum.  I would expect that one hour’s labor would be charged, and the lowest charge I would guess is $120 per hour.  I would guess $160 per hour is more realistic, so expect $180 as the total cost. For future versatility, you should consider a very high value resistor (meaning LOW loading), with the use of loading plugs to set the particular value for your cartridge; that might mean paying the technician make loading plugs. The ideal approach would be having cheap plugs of various values (e.g. 80, 160, 320, 1,000), and after ascertaining the correct value, I would hard wire a quality resistor between the positive and ground of the back of the input jack (easy to do and safer than desoldering the resistor on a circuit board which may accidentally damage a trace).

The SUT approach would require not only the SUT, but also a decent interconnect (shielded interconnect to minimize noise pickup).  This is an expensive approach and you run some risk of noise problems that are hard to resolve by finding the right location of the SUT, but, I personally like the sound of them.

If the OP wants to sell his Zephyr cartridge, I am interested. Just saying. I don’t advise it, but I’m interested.