I've already posted to Audiogon on the subject of loading in the past ('cept that I can't get the search engine to work!), but to reiterate, my approach to loading is similar to Jim Hagerman, and I recommend studying this page at length.
http://www.hagtech.com/loading.htmlWhen a cartridge delivers signal to a phono stage, the cartridge's coil inductance will react with the sum of the capacitances between the cartridge and phono stage (including cable capacitances) to form a substantial resonance peak.
Depending on the cartridge builder, part of "cartridge loading" may involve the electrical damping of mechanical resonances in the cartridge, but the truth is that at least some MC cartridge builders prefer to damp mechanical resonances mechanically and not rely on electrical means. Low-impedance MC cartridges in particular have such a high electrical resonance frequency that damping the electrical peak will not have a direct effect on the audible frequency band (such a peak could reside above 500kHz, and be 20dB or more in amplitude).
An important part of what happens when loading a low-impedance MC cartridge is to resistively bleed off the electrical resonant energy so the phono stage's input circuit doesn't go berserk and generate IMD (which we can hear). IOW, what you are primarily loading is the input of the phono stage rather than the cartridge (hence my use of quotations around "cartridge loading"). Proper loading tends to change according to the individual situation, because although the cartridge coil inductance may be the same, the cable capacitance may be different, and different phono stages have different degrees of suceptibility to RF resonances. IME, if a given phono stage combines very linear behaviour with high overload margin in the RF region, or if it has heavy input loading so that RF frequencies are effectively blocked from entry, it will audibly be considerably less sensitive to input loading than otherwise.
What you want to know is the inductance of your cartridge, and the net sum of all capacitances that lie between the cartridge coil and phono stage input (including cable capacitances). Then plug them into Jim Hagerman's on-line calculators, set the loading accordingly and listen.
Note that with MMs, MIs, IMs, high-output MCs and other higher-inductance cartridge designs, the resonant peak created by the interaction between coil inductance and cable-plus-input capacitances is much more likely to fall closer to the audible band, and chances are greater that the choice of input loading will have a direct effect on what you hear.
regards from another garage company (grin)
