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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
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cleeds
6,033 posts
 
atmasphere

... if you understand that a cartridge is a generator, maybe this idea is easier to understand in that a conventional generator which is spun to make electricity, the generator shaft becomes progressively harder to spin the more the generator is loaded. A cartridge **has** to have a similar behavior!
That's a great analogy! Thanks for sharing, Ralph!
bydlo
142 posts
 
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.
@lewm What you are describing is the fact that the lower output resistance of a voltage generator, the more current efficient it is. This does not change the fact that by the laws of induction MC and MM carts are both voltage generators.

atmasphere's avatar
atmasphere
11,973 posts
 
I wouldn't worry about whether a cartridge is a voltage or current generator- the simple fact is current does not exist without voltage and vice versa. I think this might have come up on account of current amplifier phono sections, which have that low 'virtual ground' thing going on.


Just because its a current amp does not mean you need the source to make only current.

At any rate, a cartridge makes **power** since its a generator; there is voltage and current at the same time.
lewm
13,348 posts
 
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.
intactaudio
302 posts
 
Ralph,

To be clear, a current amplifier does not significantly load the cartridge. The 'zero ohms' thing that you see talked about in reference to them refers to the virtual ground with which the cartridge plays a part.

I built a spice simulation of the circuit in question and while the input Z was not 0Ω, it was low and followed the  output V / R pattern that Lewm described.  When I placed a 0.05mv 2Ω source it delivered 25µA of current into the phonoclone circuit.

I am referring to the simple fact that a stiffer cantilever will be unable to trace higher frequencies- at some point, it won't be able to follow the groove wall impressed with higher frequencies.

I believe that if a cantilever is either too stiff or too compliant it will have issues tracking high frequencies.   As for 47K being the optimal load,  I see all kinds of manufacturers suggesting values other than 47K as the optimal load for their cartridges.  

dave
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