On another phonostage the XX2 mk2 likes around 450Ω. If you set too low
bass gets a bit flabby, too high and its tight but light and the top
end gets a bit sharp.
. The XX2 is 6 ohms so a 10x loading is appropriate. However, as others
state, tune it by ear. I tend to prefer a little less loading in general
as it tends to free up the sound.
Serious question-is unloading a MC cartridge equivalent or analogous to switching a tube amp from ultralinear to pentode/triode?
All of these comments point to the same issue. Here's how it works:
The loading of the cartridge is for the benefit of the preamp not the cartridge. The reason this is so is that the inductance of a LOMC cartridge is quite low and it won't be affected by loading at audio frequencies. What is happening is that the inductance of the cartridge is interacting with the capacitance of the tonearm cable, creating an electrical resonance at a very high frequency, which might be as high as several MHz. This peak can be energized by the energy of the cartridge and set it into excitation. When this happens (and it happens almost continuously), Radio Frequency Interference (RFI) is injected into the input of the phono preamp. This can cause it sound sound bright if the preamp is sensitive to RFI.
The loading resistor detunes the electrical peak so it can't go into excitation. No more RFI. But there is a downside- now the cartridge has to do more work, since the phono input is normally 47,000 ohms, and now you're asking the cartridge to drive 100 ohms or less. This energy is coming from the grooves- and it means that the cantilever is stiffer and harder to move with that 100 ohm load.
If the preamp is designed to not be bothered by the RFI no loading resistor is needed at all. Just plug and play. When the loading resistor is present, this can throw off the mechanical resonance of the arm/cartridge system (which is supposed to be between 7 and 12Hz) so you might experience tracking issues (more sensitivity to warp or less ability to track complex passages). You might also experience less high frequencies as the stylus is now harder to move.
If the phono section is designed to handle the electrical resonance without overload, less ticks and pops will be the result. If the preamp has loads built-in other than the industry 47K, its likely that the issue of resonance was not examined by the designer.
