input impedance load on a cartridge.

Generally, if you're loading at X ohms and its sounds a bit dull/lifeless/bass heavy that way, try higher loading to get it to even out a bit.  Alternatively, if you're loading at Y ohms and its sounds a bit too sparkly/tinny/HF heavy, then try lower loading. to get it to even out a bit.

Generally, if you're loading at X ohms and its sounds a bit dull/lifeless/bass heavy that way, try higher loading to get it to even out a bit. Alternatively, if you're loading at Y ohms and its sounds a bit too sparkly/tinny/HF heavy, then try lower loading. to get it to even out a bit.

That's correct.  Most cartridge loading pertaining to sonics will be very subtle.  The more resolving the system, the more you will hear it, but it will not change the overall sound aspect of the cartridge.

There are some that prefer loading a MC cart at 47K ohms, just like a MM cart.  I have owned a few MC carts that do indeed sound better up that high.

The end game is:  do whatever sounds the best to you.  Again, you can NOT hurt anything doing this.

To add to which it’s not just the cartridge and phono stage but also how the downstream pre deals with HF resonances. Some setups actually like the extra boost you get from a high loading while others are insensitive so you have to try it and see

The "rule of thumb" is 10X the mc cartridge's internal impedance: Denon 103 impedance is 30 ohms, so 30 X 10 = 300 ohms for best (flattest) response.

Many of the above posts are incorrect.

The reason why loading has an effect has nothing to do with the cartridge directly. It has to do with the stability of the preamp.

The inductance of the winding of the cartridge is in parallel with the capacitance of the tone arm cable. This forms a Radio Frequency tuned circuit (also known as a tank circuit). The tank circuit is set into oscillation by the energy produced by the cartridge. It often resonates at several MHz and thus produces RFI (Radio Frequency Interference). Some preamps don't like that and don't sound right as a result.

The loading resistor detunes the tank circuit enough that it will no longer resonate. Then the preamp sounds fine.

If however, the preamp is properly designed and is stable with RFI, then the loading resistor will be found to have no effect.

IOW, if you need the loading resistor to make your cartridge sound right, it points to a stability problem in the preamp.

You can find this topic discussed elsewhere on this site and others. Jonathan Carr of Lyra and Jim Hagerman have discussed it at length as well as myself. Jim has a good article online:
http://www.hagtech.com/loading.html

-which goes into the math of it.

Our preamps are stable so no loading is needed. We provide a loading strip, but it is mostly for high output MM cartridges where loading is critical and affects the cartridge directly at audio frequencies.

One additional point- when loading the cartridge, you are making it do work. This stiffens up the cantilever, changing its tracking characteristic- it will be less compliant; that's not a good thing. You are better off with a stable phono preamp.