Benz SLR Gullwing, not sensitive to loading?

That explains it. I now know why I always felt an affinity towards 47k values for my LOMCs. Even though I did start with the recommended loading values set by the manufacturer, I gradually migrated to the higher values as each time I went higher, it sounded better than the previous values. 

Even though I did start with the recommended loading values set by the manufacturer

They specify those lower loads because they have no idea what phono section will be used and the simple fact is that many designers do not take the electrical resonance I mentioned earlier into account. This causes them to be sensitive to RFI and thus the loading resistor has a very noticeable effect.

But nothing comes for free except nothing and sometimes you have to pay even for that :)  In the case of a loading resistor, 100 Ohms is 2 orders of magnitude less than 47000 Ohms and so you are asking the cartridge to do more work driving that load and so the cantilever becomes stiffer (less compliant) due to the electrical load. This can have an effect on how it behaves in the arm.

This is not about whether loading should make a difference. The key statement from the OP is:

And there is not the tiniest difference in sound at all. Plus the three tracks even have the same volume level.

If there is no change in level on a 38Ω cartridge with a 100Ω load, then there is a problem with the test methodology.  Either the applied load is not connected or the level measurements showing no change are incorrect.  Mulveling's first response pointed this out and there is no sense in going on tangents until this obvious problem is addressed.

dave

I’ve heard horror stories of bad parts lately so it may be worth confirming your 47K resistors are in fact 47,000 ohms. It does seem as if the cartridge signal is “seeing” a lower value (path of least resistance) in the circuit.