Cartridge loading

Dave, I read your post after responding to Chakster.  But I hope there will be more comments on loading and especially on "current drive", over and above the discussions you and I have had privately.  On the question of whether increasing the load on an MC might impede tracing of HF encoded on an LP, I have been wrestling with that, as you know. In my own thinking, I start with the well known phenomenon of "back EMF", as I stated elsewhere on this thread, which is a phenomenon associated with driving an electromagnetic woofer, most notably. For an MC cartridge, the groove undulations put mechanical energy into the cantilever. The coil rides on the cantilever and has its own internal resistance related to the wire gauge and the number of turns of wire.  For an LOMC, the resistance is typically low, almost always less than 50 ohms and most often less than 20 ohms. I am wondering whether spurious motion of the coil in the magnetic gap could excite a force that feeds back on the motion of the cantilever so as to dampen or impede it. Then I wonder whether the load resistor might affect the magnitude of that phenomenon. Since the coil resistance is already quite low relative to external load resistance, maybe the value of the load resistance would not make much difference, and therefore there would be not much effect on the tracking of HF. But maybe the difference between 100 ohms and 47K ohms (extreme differences in other words) is significant in terms of the magnitude of the retarding force.  Or is this pure science fiction?
If this notion has any merit, then there would be a big difference among different types of cartridge (MM, MI, etc) as to the magnitude of the effect, because cartridges that are not LOMC typically have much greater internal resistance.

As I have mentioned many times, the input impedance cannot be zero. If it were, you would have no output at all because the signal would be connected directly to ground.

While it is true that no voltage can develop across 0Ω that doesn’t mean that the current that is generated cannot be amplified and then converted back to voltage. While I agree that in reality 0Ω is an impossibility, I am also not convinced it is a good target to shoot for from anything other than an academic perspective. Like everything else in audio, the truth rarely lies at the extremes and lives in the subtleties of the middle.

As I have mentioned many times, the input impedance cannot be zero.

@lewm So the designer Junji Kimura is lieing everywhere about 0Ω inpedance of his own 47 Labs 4712 Phonocube and slightly cheaper 4718 phonostage too, and every reviewer repeating it ? I just don’t understand why then everywhere the input impedance in his special circuit stated as ZERO if it’s 2-4 Ω ? What’s the goal to tell it’s 0 Ω if it’s higher, will it help to sell more units ?

I don't accuse anyone of lying, except a certain President of the USA on some occasions. But manufacturers are sometimes given to hyperbole in their advertising copy, and too, they are sometimes inclined to treat their potential customers as ignorant, such that they feel the need to exaggerate in order to make their point.  Like Intactaudio said, an "ideal" current-driven phono would in fact present a zero ohm input Z. So I would say maybe Mr Kimura is exaggerating.  I never did any research into the 47 Labs product, but I did read as much as I could find about several others, most of which are far more costly than the 47Labs, and some of which have been given rave reviews (e.g., Aqvox, BMC MCCI, etc), and none of those truly provides zero ohms input impedance, if you read the fine print.  But that doesn't lead me to believe they aren't excellent in SQ.  In fact, I think that when M Fremer reviewed the BMC MMCI, he indicated its input Z is about 4 ohms. The one I'm using I know for sure does not give zero ohms input Z, but the sound I get from the MC2000 is superb, and that is what counts. I've also used it with another LOMC (AT ART7) that has a 12 ohm internal R.  Since my unit's input Z is about 20 ohms, it is operating more like a current drive when I use it with the latter cartridge, and it sounds just as excellent.

Dear @lewm  : """  could excite a force that feeds back on the motion of the cantilever so as to dampen or impede it.   """

Could be but I doubt it that could " impede it ". What you said is not related to the loading resistor that's what atmasphere supports alonfg its effects/? ? ?.
Now a cartridge designer/manufacturer takes in count all the elctrical and mechanical scenarios where the cartridge plays its role and seems to me that everything is really claculated witgh " wide " limits for the different play role scenarios due that the cartridge needs/must will performs good in such different scenarios. I don't rthink that in a good top cartridge design we can find out " surprises ".

In theory and due that a LOMC cartridge has a very low inductance the impedance loading ( resistor ) just can't modified ( electrically. ) the cartridge behavior. Instead in the mechanical scenario/land several and different parameters affects and has effects on the cartridge quality performance levels.The " dull " sound that some one posted when the cartridge is loaded with 100 ohms in reality is not a " dull " sound and what happened is that with that kind of load ( tha's the one I use. ) the SPL goes a little ( tiny ) lower and our ears are extremely sensitive with SPL changes especially at HF  but the information is all there and even cleaner that at 47kohms.
I attested that effect with different phono stages in many audio systems including mine.

As time goes on what atmasphere said has lower and lower and les " credibility " especially with out evidence by his part and taking in count the many first hand experiences we have that showed that things are the other way around.
You or intactaudio and other gentlemans as me are not true rookies in analog audio, we know for sure many audio main and critical subjects and if some one or something is out of the normal behavior/experiences then I want to learn two things: first if I'm wrong with all what I learned about or second to confirm that what I learned is rigth. Tha's all.

So we have to wait for the atmasphere precise and specific answer. We will see.

R.