Importance of impedance matching cartridge with phono stage?

There are many threads on this subject in these archives. Try doing a search. Personally, I’d say 20 ohms is useless with all but a very few very low output cartridges. So you’re basically stuck with 100 ohms, which is ok for most but not all LOMCs. Bad for any other types.
You should mention the gain of the phono and line sections and what cartridges you use.

A whole lot of low-output MC’s like to be loaded 100 ohms or less in conjunction with many active MC phono stages.

This statement is false (and a very common myth). The reason for the 'loading' has nothing to do with the cartridge and everything to do with the preamp's ability to deal with RFI.

The correct term for the resistor is its a 'detuning' resistor. Here's why:http://www.hagtech.com/loading.html

As you can see (from the link), the peak is a good 30dB more than the signal itself; if your phono section isn't good with that sort of RFI at its input, it won't sound right and by detuning the tank circuit at the input of the phono section relieves the preamp of the RFI so it can perform properly.


But there's more- the detuning resistor forces the cartridge to do more work and that energy has to come from somewhere- which means that the cantilever becomes stiffer and less able to trace high frequencies.


You are far better off if your phono section can deal with the RFI. A side benefit of this is you will likely get less ticks and pops, since overload margin at RF frequencies plays a role as well (IOW many ticks and pops are caused by overload, not the LP itself).


Many phono preamp designers simply don't realize that a good phono section is more than enough gain, proper EQ and low noise. It also has to have good overload margin, be resistant to RFI and otherwise be stable (and FWIW feedback or passive EQ has nothing to do with it). 


If the preamp itself has options for loading its a good bet the designer hasn't thought this through.

Thanks for the responses.  The phonostage was added for a turntable/cartridge I will get in the future, and as such I don’t know what cartridge I will get yet.  It will be my next addition to my system, and why I cannot do a test with how it sounds now.  That is why my question is whether I should care that my version of the phono board supports only 20 and 100 Ohm loads, and not the higher impedance loads of the new revision of the board.

From the responses so far, it sounds like I should be okay with this board based on the fact that 1) most MC cartridges should be fine with the 100 Ohm setting so there are lots of options, and 2) I can simply make sure I don’t get a cartridge that isn’t okay with this setting, by ensuring the cartridge has a less than 0.4mv output.

Right?  Thanks!

Dear @nyev : I know very good Gryphon electronics and are really good. Like other gentlemans posted you don't have to be worried about impedance for your future cartridge, 100 ohms can works very good with.

""  I know relatively little about analog .... """

when you receive the cartridge try that your makes the cartridge/tonearm set up for you and that you can learn about, very important this subject as it's too that you give the cartridge at least 50 hours of playing time to fine tune that set up and for the cartridge can shows its real quality level performance.


Regards and enjoy the MUSIC NOT DISTORTIONS,
R.

From the responses so far, it sounds like I should be okay with this board based on the fact that 1) most MC cartridges should be fine with the 100 Ohm setting so there are lots of options, and 2) I can simply make sure I don’t get a cartridge that isn’t okay with this setting, by ensuring the cartridge has a less than 0.4mv output. 

Yes you will be okay. But no, its nothing to do with output. Different MC cartridges sound better with different loading, but it has nothing to do with their output level. Where you care about output is if the cart is very low output, making sure you have enough gain.

The reason you don't care about the loading is its so easy to get whatever you want. Buy resistor. Swap resistor. Listen. Repeat. A little extra hassle, well worth it for the savings I would think.