Cartridge Impedance

Dear @terry9  : First than all I said that LOMC cartridges are not sensitive to load impedance changes in the phono stage and that's the phono stage whom is sensitive to those load impedance changes thatform a circuit internally and that " there " even capacitance has something to say.

I never told capacitance affects the LOMC items, it's obvious it did not. You, me and every one else knew about.

R.

@lewm  : ""  The inductance combined with capacitance introduced by the IC and by the input gain stage can cause a high frequency resonance. With LOMCs, this occurs at very high frequencies, well beyond audibility or the capacity of any speaker to reproduce, because of the low inductance and given any reasonable amount of capacitance.   ""

yes, that's what I mean with a very bad explanation and is something that's not totally proved: it's what in theory could happens. Now, we can hear nothing at the frequency that was affected or its frequency range.

As I said, LOMC are sensitive ( very ) to inductance and very tolerant to load capacitance changes.

R.

The loading is strictly for the preamp’s benefit and does nothing for the cartridge.

The reason it is there is because the inductance of the cartridge and the capacitance of the tone arm cable form a resonant circuit known as a tank circuit, which can be driven into excitation by the energy of the cartridge, creating ultra sonic or (more commonly with LOMC cartridges) RF noise.

If the preamp is unhappy with RFI injected into its inputs it might sound bright. The resistor detunes the tank circuit thus eliminating the RFI and calming things down. The downside as others have pointed out is that the loading forces the cantilever to do more work and makes it stiffer, less able to track higher frequencies.

If the preamp does not care about RFI then there is no need for the cartridge loading. But if its provided with a switch, its a pretty good bet that RFI is an issue. IME use the highest setting that sounds right.


You can find more at this link:http://www.hagtech.com/loading.html

IOW- I’m not making this up (I build phono sections for a living).


Now a side benefit of not having to load the cartridge is often that you also get less ticks and pops, since many of those are created by the phono section itself. Referring to the link above, we see that the peak I mentioned is a good 30 dB (1000x) higher than the signal itself! Yikes! If your phono section has poor overload margin, you tend to get ticks and pops on this account.

@rauliruegas

The OP is talking about loading his cartridge at his phono stage. When you post, "LOMC cartridges are not sensitive to load impedance, are sensitive to inductance changes," you imply that impedance does not affect the sound. That is incorrect.

Perhaps you meant to say, "It is the preamp, not the cartridge which is sensitive to impedance." That statement would be true, but irrelevant, as the OP wants to know how to set up his system. Compare your statements to those of Lewm and Atmasphere, who contribute to the discussion by explaining the technical details as well as addressing the OP’s point.

Dear @terry9 : "" and whom react to load impedance in reality is not the LOMC but the phono stage performance. """

That’s what I posted.


""" and makes it stiffer, less able to track higher frequencies. """

that’s not proved, it’s theory. In a normal designed phono stage you can test the MC 2000 LOMC cartridge by Ortofon that has really good tracking abilities and changing load impedances you just can’t detect " less able to track higher frequencies ". For this could happens you need that a cartridge with over 30cu goes down to 6cu ( stiffer. ) and that just can´t be happened because a normal load impedance changes. Just common sense.

Btw, the OP says: """ I just bought a phono pre-amp that allows me to adjust the impedance of a MC cartridge. I was using 100ohms. Now I want to experiment. """

what he need is to experiment with because you or me or any one else here know exactly that phono stage circuit design.

Against that reality, all our posts are irrelevant because all of us own different phono stages and room/systems. Useless, he needs to has first hand experiences and that’s all:  he has in the OP the response. My bad explanation and other only can makes that this Agon new comer can have a mix up: maybe not, who knows?.

Testing is the name of the OP game.

R.