Cartridge impedance loading question

The correct loading for the cartridge is 47K ?

There is no "correct" loading. Assuming you're going straight in, why don't you start at 100 ohms as suggested by Shelter and adjust it to taste?
http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1077125197&openfrom&1&4#1

I've used this cartridge for a number of years.
My various phono stages have all been of the moving magnet kind, 47Kohms at input. I have adjusted loading by means of different step up transformers.

For a long time I used an sut that reflected a load of 470 ohms back to the shelter, while stepping up its output voltage by 10 times. (aka 1:10 turns ratio)

And I enjoyed the cartridge quite a lot at this loading.

I have also loaded this cartridge at 209 ohms by using a sut with a turns ratio of 1:15.

With regard to your options with the Black Cube I'd try it at both 100 ohms and then 470 ohms. Choose between those.

I haven't tried it, but it has been suggested to me by someone who has that a 1000 ohm setting works very good with the 501-II. For me that would require an SUT with a 1:5 turns ratio.

My phono stages that I have used with the Shelter have been tubed, except for a couple that I tried for brief periods and returned. I haven't tried the Black Cube.
Current stage is a Hagerman Trumpet which I find quite ageeable with the rest of my signal chain.

And, of course, your mileage might (and probably will) vary.

-Steve

-Steve

There is no "correct" loading. Assuming you're going straight in, why don't you start at 100 ohms as suggested by Shelter and adjust it to taste?

I take it from this an other comments that my post was not read through completely! So, to reiterate in other words:

The correct loading for any cartridge will be such that it does not ring at audio frequencies- IOW if you run a squarewave through it, a squarewave will come out with no ringing.

With any LOMC cartridge ever made, this will be the case at 47K. So why do we hear differences? It has not so much to do with the cartridge and **everything** to do with the phono preamp. If the preamp is sensitive to Radio Frequency Interference, then loading the cartridge will affect tonality as it detunes the RF circuit formed thus:

The RFI (Radio Frequency Interference) is caused by the excitation of the RF circuit formed by the cartridge inductance and the capacitance of the interconnect cable. The loading detunes the circuit so the RF bursts cannot occur.

-as I mentioned earlier. IOW, if loading is audible in your system, your phono section is sensitive to RFI.

Please note that the correct loading value for such a preamp cannot be predetermined since the cable is part of the RF circuit and its capacitance will affect the value. If the manufacturer of the cartridge recommends a particular value, it simply means that *their* reference preamp has troubles with RF and nothing more. But you will find that most manufacturers recommend 47K as it is correct.

* The correct loading for any cartridge will be such that it does not ring at audio frequencies- IOW if you run a squarewave through it, a squarewave will come out with no ringing.*

Ringing at audio frequencies might be a your criteria for loading an MP-1, but there are certainly other considerations for the rest of us, and I would think for MP-1 users as well. That is the sound, irrespective of RFI.

That bit about squarewaves is cute, but would leave a lot of people scratching their chin and changing load. I'm not saying your criteria is irrelevant, but it's not the ONLY criteria.

* With any LOMC cartridge ever made, this will be the case at 47K. So why do we hear differences? It has not so much to do with the cartridge and **everything** to do with the phono preamp. If the preamp is sensitive to Radio Frequency Interference, then loading the cartridge will affect tonality as it detunes the RF circuit formed thus*

Changing load does not necessarily affect tonality. The highest value or 47K is often not the most desirable. BTW, why stop at 47K, why not 1M or infinite?

The answer has to do with how the phono stage reacts to RFI as I have pointed out.

Designers also have to be pragmatic about what sort of input impedance is needed to control noise! If it were to be high as you ask about, controlling noise becomes a major problem in a high gain circuit! So 47K was derived as a reasonable compromise decades ago- it allows low noise and a moderate, easy load for almost any phono cartridge.

Ringing at audio frequencies might be a your criteria for loading an MP-1, but there are certainly other considerations for the rest of us, and I would think for MP-1 users as well. That is the sound, irrespective of RFI.

To be clear, 'Ringing at audio frequencies' is no more a consideration for our preamp as any other, as such only occurs with high output moving magnet cartridges. For them, the inductance is much higher and so loading is important.

Regarding the sound, it cannot be considered 'irrespective of RFI': in plain and simple terms if the circuit has RFI problems **the sound will not be right if RFI is present!!** If such is the case then loading will have a beneficial effect.

In more detail: if the circuit is sensitive to RFI, due to poor layout, lack of input stopping resistors, RFI filters, bad grounding (IOW anything that can cause RFI sensitivity), etc., the result will be that RFI will adversely affect the sound. The RFI is generated by the pickup and cable itself: it is not a matter of shielding from radio stations.

Until this fact is understood loading will remain mysterious and a matter of debate.

Ringing and squarewaves is not just cute, it is part of the toolkit one uses to do circuit analysis. It might interest you to know that many years ago I tried to make a box that one could simply plug in the phono cables from the arm and the box would sort out what the right loading was. It was during experimentation to gather data that I saw that LOMC cartridges don't ring at any frequency anywhere near the audio range- in fact even with a 100KHz squarewave to 'ring' them, they still just pass the squarewave perfectly. Once I understood this fact, I was then able to make changes to our preamp design to make it more RFI resistant at its input, which had the effect of making the low impedance loading resistors nearly irrelevant and also improved the sound at the same time- that latter bit of course is what we are all after.

So loading is not about LOMC cartridges and it is entirely and 100% about good circuit design in the phono preamp.