Cartridge loading

Raul, Likewise, I wrote the above post before I saw your response to Dave.  No problemo.

For the record, I did mention the relationship between the input impedance of the Intactaudio device and the output Z of my MC2000 (2 ohms into 20 ohms), by way of speculating on how it is working with that particular cartridge. Nearly any very LOMC cartridge with a very low internal R would tend to work with the IA device in a voltage-dependent manner, I guess.  Still, the IA device also sounds great with one of my other LOMCs that has a high-ish internal R and where the amplification would be more in the current domain.  (Dynavector 17D3 which has internal R = 32 ohms.) Be that as it may, I am driven to try out a very very low input impedance phono some time, with the MC2000, just to satisfy further my curiosity.

Raul, When IA used the term "tests", he meant exactly that.  He made measurements using the proper test gear and said nothing about listening tests.  Not that there is anything "wrong" with either approach, except I would posit that subjective testing based only on listening is fraught with error, not the least of which is error due to listener bias.  Furthermore, Dave (IA) was not per se testing Atmasphere's hypothesis that low resistive loads impair HF tracking.  He was testing a finding put forth by Moncrieff, to the effect that unloaded LOMCs (i.e., with a 47K ohm load) exhibit a form of IM distortion (when he used one particular pair of frequencies for his IM test) and that the distortion is reduced when you use progressively lower resistive loads, down to 100 ohms. Nevertheless, Moncrieff's and Dave's measured findings might (or might not) provide a scientific rationale for your position.  As for me, I wonder about the particular pair of frequencies that Moncrieff used for the IM test and whether one might get a different result for other pairs of frequencies.  (I think the upper one was 4KHz; would that be high enough for the effect described by Atmasphere to kick in?) Or for different cartridges.  (I don't know what cartridge was used by either Moncrieff or Dave.)  Finally, I personally wouldn't care if using a 47K load produces a bit more measurable distortion, as long as the result sounded closer to live, real music compared to a 100R load.

Raul, Intactaudio made measurements of frequency response and IM distortion, I think. You are here reporting your subjective impression, which is fine, but there’s a big difference. 

I was merely pointing out that there is some merit in this idea of a "current-driven" phono stage for certain very LOMC cartridges, even though the use of the term may be semantical or to put it another way, an exaggeration.  On a practical level, I hear it.  I was maintaining a priori in my discussions with Chakster that the input impedance of most such phono stages, or phono stages that have been marketed as "current-driven" is not zero.  So I don't disagree with any of the above. The key word is "marketing". Anyway, I am quite pleased with the result.

bydlo and larry, I wouldn't argue with what you both say, but I would point out that the capacity of a LOMC to make signal current into a very low resistance load (meaning a load that is equal to or much lower than its internal impedance) does not usually parallel its capacity to make voltage into a "high" resistance load (meaning any load that is about 10X the coil resistance). (I am not getting into the argument between Raul and Atma-sphere.)  For example, my MC2000 is rated for 0.05mV at the standard stylus velocity.  But its internal resistance is only 2 ohms. Thus it can generate 25uA of current into no load or probably anything much lower than 2 ohms.  For comparison, my Audio Technica ART7 has twice the voltage output of  the MC2000 (0.12mV) but also has an internal impedance of 12 ohms at 1kHz.  Thus the ART7 is less efficient at generating current (10uA), when forced to do so, than the MC2000.  Viewed this way, the MC2000 more than holds its own for current output, among very LOMC cartridges. So, I think the point of a "current-driven" phono stage is that it might be advantageous compared to stages that are voltage driven, only for certain very LOMC cartridges.  It certainly has been demonstrated in my system with the device made by Intact Audio. No one views the idea of current-drive for phono as a panacea for all LOMC cartridges, but the flexibility is there.

Chakster, I am experimenting with a device made by Intact Audio.  It's a prototype, one-off, not in production.  It's "based on a Nelson Pass I/V converter for current output DACs", according to Intact Audio.  It is not a phono stage per se; it is inserted into the chain between the LOMC and the input of an MM phono stage, or any phono with a 47K input resistance (I guess).  The output of the IA device drives the MM input of my Manley Steelhead, set at 50db of gain. (There is no added gain from the high level section of the Steelhead.)  No hiss or otherwise intrusive noise or hum allows me to appreciate the MC2000 for the first time. (I don't own the T2000 SUT or another SUT with similar characteristics.) 

Chak, Is THIS what you have?https://audiocubes.com/products/47-laboratory-4712-phonocube

Hey Dave (Intactaudio), .001 ohms is still not zero ohms.  I'm just sayin'...But I'm also impressed.  That unit can do the purest "current gain" of any I know about so far.
And, since Chakster can move at light speed, rules fall apart.

Raul, I share your interest in this subject.  But I also know that Intactaudio is one of the smartest guys in the business, even including the persons you have in mind, and I know that he is still thinking on this subject of the effect of load on the motion of the stylus.  I see it as a very complex question, but maybe that is because I myself am so lacking in understanding.  However, as I understand you, your position is that it doesn't happen, because you can't hear it (and because you have the testimony of some other knowledgeable persons who also deny the phenomenon exists).  Is that a fair summation of your position?

Raul, I have no idea what you are trying to say.  Please clarify. Thanks.
From the one sentence I think I do understand, how can one subtract the effect of the load resistance when the entire question revolves around the value of the load resistance?  Ralph says that low value load Rs tend to impede the cartridge's ability to trace HF.  My idea, for good or ill, is an attempt to explain how that might be the case, but I am saying that the load resistor, for an LOMC, is in parallel with the coil resistance, which is already usually less than 20 ohms.  So the parallel sum of the value of the coil resistance plus the load resistor will always be less than 20 ohms.  In other words, the load resistor does not make a big difference and maybe therefore should not have much effect on the magnitude of any "back EMF" generated at the coil/magnet interface.  This would lead me to disagree with Ralph, but the whole issue is a bit over my head to begin with, and I seek input from others who know more than I do.  There's another way of looking at it, too.

By the way, I don't think cost is a factor in achieving the lowest possible phono input impedance, if that is the primary goal ahead of performance. I also see that I earlier already suggested that the BMC MCCI affords a 4-ohm impedance.  I am not certain that is correct, but there is one out there.  MCCI is quite low, though.  Meantime, I am waiting for someone to jump on my hypothesis about the effect of load resistance on the capacity of a cartridge to trace HF.  (This has nothing to do with current drive vs voltage drive.) I'm pretty sure I am off the mark.

Saying that a (working) phono stage has zero input impedance is similar to claiming to travel at the speed of light or to live forever. It’s a physical limit that one can only approach but never reach, if one actually wants to hear music come out the other end. 1-2 ohms might be possible. I think one unit I investigated got down to 4 ohms.

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.

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.  That condition (zero input impedance) is in effect a mute switch. Most "current driven" phono stages that I have investigated in detail, so far as that is possible, because most manufacturers are secretive, have an input impedance of 4 to 20 ohms, depending upon the product.  I am using one now in conjunction with my Ortofon MC2000 that has an input impedance of 10-20 ohms.  With such a value, and given that the MC2000 has an internal resistance of only 2 ohms, you would think the input is voltage driven, in fact, because the ratio of the two impedances is favorable (about 1:10 ratio).  I don't know how it works (current or voltage), therefore, but it works fantastically well, allowing me for the first time to hear the MC2000 and without an SUT.  I have never owned an SUT.

Raul, You could make a useful contribution to the thread by describing why you (apparently) think Ralph is incorrect in his statement that low resistive loads on an MC cartridge can impede its ability to trace HF. 


And by the way, in the American/British idiom, calling someone a "lier" (by which I think you mean L-I-A-R, i.e., a person who lies), can correctly be categorized as an insult.  Insults are the basis for a verbal "attack".  Thus it can be said you attacked Ralph.  You can't have it both ways.  If Ralph is incorrect in his thesis, that does not constitute a "lie" in any sense. He is stating what he believes to be true, right or wrong.

No, you have a big problem. Not me.  Wanna go back and forth on this? I cannot imagine why you think I hit on you simply by pointing out a possible mechanism for one effect of loading on an MC cartridge. I was trying to make a neutral contribution to this discussion, but I realize it may have seemed to you that I was taking Ralph's side against your attack. I really wasn't.
Thanks for the correction on the recommended loading for the Lyra cartridges per the Lyra website, but is it not the case that Jonathan Carr has suggested 47K ohms for LOMCs, in this forum?  If I'm wrong there too, I would like to know about it.  In any case, I am far from "recommending" a 47K load.  As you may recall, I discovered that I liked 47K for one of my LOMCs by accident, because I forgot to adjust the load at the phono input one evening before playing music.  So I reported my surprising result here.  Unlike yourself, I do not try to tell other people what they should do. And the cartridge was not riding in either of the two tonearms that I own and you hate, on the evening when I made the observation that there is some merit to 47K loading in my system.  And why does THAT make you so furious?

On my post to which you responded (today at 1:18 pm), I was typing on my iphone, on which I am prone to errors. Perhaps the grammar of my sentence confused you, and I was unable to edit it because Dave (Intactaudio) posted before I could make a change.
So, my sentence, "But you have absolutely no grounds to say that a 47K load on a LOMC cartridge sounds best to me in my system in my house with my equipment", should have been re-written to say that you have no grounds to doubt my observation that 47K sounds best, in my house, in my system, with my cartridge. (I think at the time I was using either my Koetsu Urushi or my ZYX Universe.) I certainly did not mean to deny the fact that I did make that observation. Yes, that is what I have found with one of those two cartridges. As of today, I would say that loads above 1000 ohms, up to 47K ohms, sound about the same, but below 1K sounds less "real", more closed in. I’ve never checked the actual frequency response. Nor did I ever claim that high frequencies were actually attenuated with loads below 1K ohms. I am reporting a subjective judgement of what I hear on music. So keep your shirt on.

By the way, I should add that when it suits you, you are quite willing to accept J Carr as a guru.  Yet JCarr is one of many of the cognoscenti who also suggest 47K as a load for LOMCs, especially the Lyra cartridges he designs.
So now, what’s your problem?

 Raul, it may shock you to learn that my credibility with you or lack thereof is not a matter that concerns me a great deal. We disagree on many many things, and you know that.  But you have absolutely no grounds to say that a 47K load on a LOMC cartridge sounds best to me in my system in my house with my equipment. Your system is almost a direct antithesis of mine to begin with, and you have never been in my house. Here it is not even a matter of disagreement. I seek understanding, and I am getting some understanding by reading the posts of Palmer, Ralph, and Dave Slagle. Perhaps I could thank you for being provocative, so I can learn from those other  persons.  The only thing I can be said to have contributed to this discussion is the concept that there must be a back EMF generated at the coil of a cartridge, just like the back EMF that is generated at the coil of an electromagnetic loudspeaker.  There seems to be general agreement that that is the case. After that, I am all ears and I do not pretend to be a source of knowledge. Yes, Ralph is my friend, and so is Dave. That has nothing to do with anything.

Raul, with due respect, I don’t think you took the time to understand what I wrote about damping. Since then, Ralph, Dave, and a third person have pretty much corroborated my idea, although all 3 explained it at a more sophisticated level. Thanks to them.

I think it’s analogous to “back EMF” that affects the interface between amplifier and electromagnetic speakers. The movement of the coil on the cantilever that is excited by the groove is not perfectly damped. Any spurious motion thus created would generate a voltage. The load resistor affects the degree to which the spurious motion of cantilever is damped out. Why is it hard to imagine that the damping force makes the cantilever also do more work?
But I’m just guessing pending an opinion fro Ralph or Dave.

Now try 47K and work downward from that value until you’re happiest.