Calculation verification please

Magnets and their proximity to the coils plus core material must be how they do it. The math for such calculations is complex, and I don’t know the equations. So off the top of my head, I can’t be amazed unless I knew the math and physics involved.

By normal convention "40/40" means 40 divided by 40, which is 1.  Just so not to confuse anyone, you probably meant 40-squared or 40 X 40, or 1600. 600,000 divided by 1600 (or 600,000/1600) equals 375 ohms, the load that Skos desires. I know you know that but some might have been confused by the way you wrote it. That Rogue with a built in option for a 1Megohm input impedance on its MM stage would work too, but 47K works as well.

Good point overlooked by me and everyone else: What LOMC requires a 1:40 SUT? If you guessed correctly that it is a Mysoniclabs with 0,5mV output, then your point is very well taken. 20mV of signal voltage at the standard stylus velocity will definitely overload nearly any MM phono stage, because the stylus velocity can go way higher than the standard 3.54 cm/sec or 5.0 cm/sec (the two standards for which cartridge output is calculated).  To justify a 1:40 SUT, you would expect that the cartridge output is not more than 0.15mV or preferably less.

My wife is a brunette and I don't have the gut that guy has, but otherwise there is some relevance.

Atma, Skos wrote: "I’ve been experimenting into a MC section and the manufacturer says to load between 100 - 800 ohms. I’ve tried 250, 324, 368, 404, 500 & 600 ohms and found I like best the 368 ohm loading. So now want to try using my SUT."

IOW, he heard differences in SQ among those listed load resistances BEFORE he decided to implement a SUT. So, using a step-up had nothing to do with his observation.  So many hear differences using load resistances that differ by only a few tens of ohms that I am convinced the observations are valid.  I just don't hear it, or better to say I do hear subtle differences between widely different loads (e.g., 100 ohms vs 47K ohms, with LOMCs that can drive 100 ohms) but none worth a damn. In those cases I slightly prefer 47K ohms. I do think my system is low enough in distortion that I should hear it if my brain says it's there.  That suggests my ears and brain are tuned differently or are superannuated or both.

In addition to what I and Atma have written, I am most amazed that you hear differences in SQ among resistances of 250, 324, 368, 404, 500 & 600 ohms. I don't doubt you, but I have tried such experiments and never heard much if any difference.  Or to put it another way, if there IS a difference among such closely related values, it is so subtle as to be irrelevant.  I set up one of my phono stages to be switchable between 100, 1000, and 47K ohms for LOMC cartridges.  Now I do hear slight differences between 100 and 47K ohms, but both are acceptable and close to being the same.  If I had to say, I would say 47K is slightly more tipped up toward the treble.  This is with cartridges that have internal resistance between 2 and 12 ohms. This phono stage is balanced and the cartridges are hooked up on balanced mode always, straight through to the speakers. (Balanced phono, linestage, and amplifiers.) Speakers are full range ESLs.

I must have misunderstood from the get go. I thought your original question was what parallel loading resistors would create a 375 ohm load.  Answer is still that it's not possible by introducing a resistor in parallel with 47K. I personally would do nothing; just run the cartridge into the 30 ohm load.  On the other hand, I don't know why you cannot change the load resistor from 47K to 600K, but I take your word for it. I don't think there would be anything magical about 375 ohms anyway.

I refuse to read the gibberish, but if you place a 51K resistor in parallel with a 47K resistor, you will get around 24K resistance. If you use your 1:40 SUT into 24K resistance, you will end up with a phono load of about 15 ohms. In other words, you’re going backwards. I don’t care what the book said. But your cartridge can drive even 15 ohms. So if you do the 51K mod, it will work ok, but the load is not 375 ohms. The only way to increase the resistance of a resistor is to place another resistor in series with that resistor, and obviously you don’t want to do that in this case.

just for the fun of it, if you have an ohm meter, and if you have two 50 K resistors, place them in parallel and measure the resistance across the parallel pair. It will be 25K ohms.

what you could do is replace the 47K load resistance with a 600K load resistor. Then using your 1:40 SUT, the cartridge will see 375 ohms load.

Not possible. With a 1:40 SUT into 47000 ohms, the cartridge will see a -30 ohm load. The sum resistance of two parallel resistors cannot exceed the value of the lowest value resistor. So any resistor you place in parallel will reduce the impedance, not augment it. But if your cartridge has internal resistance of 1.4 ohms, it will drive 30 ohms. So why do you want 375 ohms?