@krelldog
If the cartridge needs loading below 47K its an indication that the preamp is not stable with Radio Frequency Interference (RFI) at its input.
The loading resistor is not for the cartridge, its for the preamp.
This is because the cartridge inductance combined with the tone arm cable capacitance forms a tuned RF circuit- which is energized by the cartridge signal. It can be over 30 db higher than the phono signal- thats about 1000x more powerful!
The loading resistor detunes the RF circuit, preventing the RFI. The problem is that in so doing, the cartridge is asked to perform more work as it has to drive the lower resistance. This makes the cartridge cantilever stiffer and less able to track higher frequencies. This is why the resistor can act as a tone control.
A side problem is that preamps that have problems with RFI are also far more likely to produce ticks and pops. This is often due to poor overload margin, since a signal that is 1000x more powerful can overload the preamp. The other reason is that the phono circuit can be unstable and react poorly to RFI; either way if the phono section does not have these problems, a side benefit is far less ticks and pops- you may not ever hear any on an entire LP side.
Many phono preamp designers don't realize the RFI implications and so don't know to make sure their circuit is immune to these problems. So instead you see loading switches and the like...
