Question about Cartridge Loading

Raul, It’s not my rule. It’s just physics. If you load a cartridge that has a 45R internal impedance with a 100R resistor, of course it will work. But a large fraction of the cartridge voltage output will be lost to ground and you will lose some HF bandwidth. These two numbers can be precisely calculated but the end result is more complex because of frequency dependency. If the net result sounds best, I am not about to quibble, but if a novice asks me a question about loading, I feel obliged to tell it like it is. Then let the other guy decide for himself.

As to the importance of inductance in the Hegerman calculator for LOMC cartridges.  Did you add in say 10-20 microHenries for an LOMC, or whatever is the value for any particular LOMC?  And does it make a difference?  Of course it will perturb the value a bit, but not by any important amount.  Tell me what you found out.

It's not that 450 ohms is "optimal".  It's that you want the phono stage input impedance to be at least 10X the internal impedance of the cartridge.  In your case, 10X = 450 ohms.  So any input impedance equal to OR GREATER THAN 450 ohms would comply with the conventional wisdom.  If you don't hear a difference between 100R and 450R, I suggest you try 1000R or even 47K.  Also, check the VTA for your cartridge.  If the tonearm is not level with the LP surface, is the pivot lower than the headshell?  That can cause loss of HF response.  Also check for any number of other things that can affect HF response.

For LOMC cartridges, where the typical inductance is less than 50 micro-Henries, and often much less than that, does it really matter much to include inductance in the calculation?  I doubt it.  We saw a month ago that for the low output MI cartridges like Sussuro, which has an internal R of only 10 ohms, inductance surely does matter, because it's about 1000X higher than for a typical LOMC.

No. Loading is inversely related to the R value. The higher the R, the lower is the load on the cartridge. For an MC cartridge, the rule of thumb is to choose a load resistor value that is 10 times the internal resistance of your cartridge. If you don’t know the internal R of your cartridge, you can look it up on line. For a low output MC cartridge (LOMC), the typical internal resistance value will be anywhere from 2 to 20 ohms. A typical LOMC cartridge with a 10-ohm internal resistance will be properly loaded by a 100 ohm resistance OR HIGHER. There is no real rule for what value might sound best. Thus you may read that some like to load their LOMC cartridges at 47K ohms, which is the standard load for a Moving Magnet (MM) type cartridge but also works fine for MC. You will also read that this or that person swears by some other value in between 100 and 47K. Take it or leave it. You don’t want to go below 10 times the internal resistance for two reasons: (1) As you go below 100 ohms for our hypothetical LOMC, you will gradually be losing more and more signal voltage to ground. This reduces the usable gain of the cartridge, and (2) likewise, lowering the load R below 100 ohms will also cause a high frequency roll-off that dulls the sound of the cartridge. Again, that is a gradual phenomenon that gets more and more apparent as the load R approaches the internal R of the cartridge. This is a simple explanation. I hope it helps.