muovimies
Super Member
I don't think loading/ohms specs are crucial with a head amp, as they are with transformers. I do believe it will work fine with all MC cartridges.
SUTs, on the other hand, need careful impedance matching. I have never heard a SUT, unfortunately, as some say a well matched one with a good phonostage sound spectacular.
To be honest, I find messing with the resistive cartridge loading for MC carts to be vastly overrated, as long as the load resistance is high enough (10x is generally a good rule of thumb, 5x is usually well enough, at about 3x it starts to get hairy in my experience, but depends on the cart and phono stage / SUT / headamp also). Also IME it's actually the opposite to what you state, generally speaking with SUTs it seems to be more forgiving.
As for loading, when you start to go lower from 10x times the cartridge impedance, somewhere around 5x and lower the sound starts to subtly change, until those changes become less than subtle, at which point it usually sounds like crap already... so yeah, there might be a 'sweet spot' there, but generally speaking it's actually MM cartridges with which both resistive AND capacitive loading matters way more. It's just your average MM cartridge user is not as "discerning" about ultimate sound quality, while the more audiophile types into expensive MC carts and the like will generally be more about getting everything "just right", which has probably lead to the common perception that with MC cartridges loading matters somehow more than with MMs.
At least that's my take on the subject.