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The difference between Moving Magnet / Moving Coil / Moving Iron Cartridges

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On 8/23/2020 at 4:15 PM, MC39693 said:

Direct drive vs belt drive vs idler? Thinking of getting back to vinyl after 12 year absence... too many choices! 

Direct drive made most sense to me so I got a Technics SL-1210 GR.

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Now, after much about TT`s , cartridges and Phono-Preamplifier was reported it´s now about the optimal capacity values for MM / MI  and MC pickups.

 

MM Cartridge / MI Cartridge

In an MM system we do not need to worry about the terminating resistor. MM inputs are always terminated with 47 KOhm. There is nothing for you to do. A MM system can react sensitively to a completely wrong capacitance value of the connected cable. Here the complete cabling counts - starting with the small plugs at the pickup to the RCA plugs and everything in between anyway. The sum of all capacities is decisive .A value of 150pF is considered optimal and at the same time maximum. Real tonearm cables therefore usually have very low capacitance values.

 

As long as the overall result remains below 150pF, you will find that everything is fine in terms of sound. If you want, you can adjust this value exactly, but you should not expect too much from it. However, if you are running an MM system and you have the impression that it runs far away from its sonic capabilities, you should have the cable measured or have a look at the technical data. Maybe the capacity of the cable is too high after all and maybe this is the reason for a not so great sound.

 

MC cartridge
With the MC system, the requirements are reversed. Here the capacity value is not important. The correct terminating resistor is all the more important. If it is not correct, this may have an effect on the volume (one pickup more with the next less), as well as on the electrical damping of the needle carrier and thus on the overall sound.If an MC pickup is finished with a too low value, its sound image looks "more tired" - but it gains spatial depth. If an MC pickup is terminated with a too high value, it sounds "thinner", "harsher" and simply "nervous".

 

The value from when this resistance is "much too high" depends on the pickup's own internal resistance. With some pickups 300 ohms is already enough - with others you have to go to over 2,000 ohms. From this value nothing changes in sound. So whether we use 2,000, 20,000 or the 47,000 ohms of the MM input is completely irrelevant. In the technical data of the pickups there is usually an exact value given, which you should keep to. Otherwise, just experiment a little.

 

Can I measure the capacitance of the cable myself?

 

It is easier than to measure by looking at the technical data of the cable. If they are below 100 pF/m and the cable is not longer than 39,37 ", you do not need to worry.
However, if you have a suitable measuring device and know how to use it, measuring is no magic trick either. Just remember to take off the shoes on the pickup before measuring.

 

 

 

 

 

 

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