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Cartridge loading

Presently I am using a ZU/Denon DL103 mc cartridge with ZU Audio's highest tolerances.  I had this cartridge mounted on my VPI Prime and after going through all the various loading combinations, I settled on 200 ohms.  I was always satisfied with my choice of setting.  I no longer have the Prime and now use the Technics SL1200G turntable.  After having the same cartridge mounted and aligned by the dealer, I inserted it into my system and enjoyed the sound immensely, never touching the 200 ohm setting.

Yesterday I was listening to vinyl most of the day and for some reason I found the sound to be better than ever, mostly in the treble area.  The highs had shimmer when needed and I had played the same records many times before on the Prime and they never sounded as good as they did yesterday.  Just for the heck of it, I checked the cartridge loading and found it was now set at 1000 ohms.  As I said, when I put the Technics into the system, I never bothered changing the loading which was at 200 ohms as it was the same cartridge, just a different turntable.

I believe I know what happened, when I last used the tone controls on my McIntosh preamp, (you have to shuffle through a menu) I must have inadvertently put the cartridge loading at 1000 ohms.  It truly sounds fantastic, better than I ever thought possible.  The Bass is still very deep and taut, midrange is the same but the treble, oh my, so much better.  Now the million dollar question is why should it now sound better at 1000 ohms, when it sounded great before at 200 ohms?  Can the tonearm on the Technics have an effect on cartridge loading?  I always thought it was all dependent on the preamp, amp and speakers.  What am I missing here?  I am very curious to know.  The specs for my cartridge say greater than 50 ohms for loading.

Thanks
stereo5
intactaudio
303 posts
 
To add to what I mentioned above, The big wrinkle that got me interested in all of this is the trend for current amplification that pops up every half a decade or so.  The story goes something like this.... 

 A MC cartridge is inherently a current generator and the best way to get the ultimate performance out of it is to treat it as such and feed it into a current amplifier.  

By definition a true current amplifier would load a cartridge with a dead short which is about as far away from 47K as you can get.  With all of the discussions of how loading a cartridge has negative effects, one has to wonder how these current stages could possibly work.  There are many reports that they do indeed work, and work quite well.  It wasn't until I came across Moncrief that a possible reconciliation of the opposing viewpoints was possible for me.



dave
chakster's avatar
chakster
6,144 posts
 
A MC cartridge is inherently a current generator and the best way to get the ultimate performance out of it is to treat it as such and feed it into a current amplifier.

By definition a true current amplifier would load a cartridge with a dead short which is about as far away from 47K as you can get.


The current injection phono amp is 47 Labs Phonocube (input impedance is ZERO aka "0" )

The current source power amp is First Watt F2J and probably the one and only current source amp on the market, only 100 units made by First Watt. 

I have both in my system
lewm
13,476 posts
 
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.
lewm
13,476 posts
 
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.
intactaudio
303 posts
 
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.
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