The exercise of phono-cartridge loading is a necessary and inescapable adjunct to fully appreciating the LP experience.
Please understand, the loading of a phono cartridge and particularly that of a moving-coil cartridge is a very inexact science; specific recommendations should be taken (and offered) very lightly.
You are encouraged to think independently of the cartridge maker and to listen, choosing your loading values by ear, and using the maker’s suggestion only as a starting value.
The cartridge manufacturer may have anticipated a transformer being used for the initial stage of gain. With active circuit elements, cartridge loading becomes a very different proposition.
As an added complexity some tonearms use special high-resistance wiring, which must be accounted for in this load selection. The same thinking applies to the sonic effect of interconnects from turntable to phono stage. You must think and act globally.
A carelessly or improperly loaded phono cartridge will suffer every sonic anomaly imaginable, ranging from lack of definition and bass to a very strident, screechy and unpleasant high end, perhaps eerie silence.
Cartridge loading is a compromise between what works best for the cartridge and what sounds best to the listener. Specifically, we are looking for that compromise in loading which sounds most natural across the whole audio spectrum for the widest range of LPs in your collection.
I suggest that you start by using the cartridge maker’s numbers as your starting point. If they give you no suggested loading, then please select a resistive value roughly 10 times the cartridge’s impedance. If working with a moving-magnet or moving-iron cartridge then 47k-ohm is the usual default value.
Always turn the volume on your preamp to a minimal setting, or your power amps off, before making any adjustments to the loading of your phono stage.
As an example, lets assume you’ve determined from a manufacturer’s literature that your cartridge has an impedance of 13 ohms, and you’ve selected 100 ohms as your starting point and set your phono stage accordingly.
Select your suite of test LPs carefully. Hopefully, it is a collection you know quite well. Pick some recordings that have known flaws you can identify and some LPs that are simply very well done.
Listen to the system for a period of time (10 minutes to an hour) using various musical selections in your standard suite. Listen until you have a good mental picture of the soundscape. Make notes.
Now, turn the volume down or the power amps off. Pick a new loading, one or two steps removed from the previous loading, larger or smaller as you deem fit (though it really doesn’t matter).
Power the system back up, re-establish the previous level setting and re-run the listening test with the same material. What comes out will either sound better or worse. If better, your new setting was in the right direction. If it sounds worse, you should have gone the opposite direction with your cartridge loading exercise. Make corrections and REPEAT, REPEAT, REPEAT!
This is going to be a simple iterative process: you identify a trend where the sound improves as you change settings. Then you follow that trend until the improvement starts to fall off. The ideal setting is then one, possibly two steps back from the point where the settings caused diminished performance.
When you find your personal best setting, you will have balanced spectral balance against spatial detail and dynamic contrast.
If you’re a rabid audiophile, you’re not quite done yet. At this point, you will be looking more carefully at the mechanical artifacts of phono-cartridge optimization: tracking force, VTA (vertical tracking angle), azimuth. Once those things are optimal, then you should go back and peak the loading back up again.