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Thread: Technical Cartridge Question

  1. #1
    Join Date: Feb 2016

    Location: Melksham, Wiltshire

    Posts: 726
    I'm Peter.

    Default Technical Cartridge Question

    Please don’t confuse me further by confusing replies.

    Is there an aficionado on the forum that can explain Cartridge loading?

    My current installed cartridge is the Benz Wood SL. I have had this cartridge for a while and always run it via the Whest PS 30 RTD at 100 Ohms 65db gain, which appears to be fine as the spec sheet says ... 0.4v >100 Ohms.

    Does >100 Ohms mean this is the minimum loading. I only ask ask, as for the sake of curiosity, I increased the loading to 220 Ohms and it sounds much better but still doesn’t define the upper limit. Confused to say the least.

    There are many other settings, I.e. 470k, 1k, 15k (47k I guess is for MM Cartridges)

    I am but a poor mechanical engineer and do not understand why this should be so...

    Can anybody explain?

    Thanks in advance

    Peter



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  2. #2
    Join Date: Apr 2012

    Location: London

    Posts: 685
    I'm James.

    Default

    The general take is that as long as the loading is at least 10x the cartridges internal impedance you will be loading it correctly, and if the spec. sheet says 100 ohm is adequate then it well be. This does not necessarily mean that the cartridge is loaded optimally though, so if you find 220 ohms sounds better then it is. And it's fine for the cartridge as well, as are higher impedances.
    There are arguments about loading affecting high frequency resonances, but I'd say if it sounds better it is better ☺


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  3. #3
    Join Date: Feb 2016

    Location: Melksham, Wiltshire

    Posts: 726
    I'm Peter.

    Default

    Thanks for that. The spec sheet says >100 Ohm. ( doesn’t that mean “Greater than 100 Ohm.?) or have I got my <> round the wrong way.


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  4. #4
    Join Date: Jan 2009

    Location: Essex

    Posts: 31,853
    I'm openingabottleofwine.

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    The SL has a coil resistance of 12 Ohm, so ideally the loading should be not less than 10x that figure, that is >120 Ohm. 220 Ohm ought to be fine.
    Barry

  5. #5
    Join Date: Apr 2012

    Location: London

    Posts: 685
    I'm James.

    Default

    Yup, you're both spot on

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  6. #6
    RothwellAudio Guest

    Default

    Yes, > 100 ohms means greater than 100 ohms, so it only sets a lower limit. Most LOMC cartridges are specified that way with only a lower limit. In theory anything above the quoted figure should be fine and make no difference to the sound but in practice some people find a subtle improvement with a higher figure than the minimum. Some people claim that one particular load value makes the cartridge sing and everything else sounds terrible but I suspect they're exaggerating.

    The usual explanation is that the inductance of the cartridge's coils produces a peak in the frequency response and the load impedance tames the peak. However, doing the maths with some typical cartridge specs makes this explanation less than convincing.
    Another possibility is that lower load impedances draw more current from the cartridge and that current flowing through the coils produces a back EMF which damps the motion of the coils. It's the same principle as a power amp with a low output impedance damping the coils of a loudspeaker. However, once again the maths doesn't prove this theory entirely convincingly because the damping effect of the stylus suspension swamps the effect of the current in the coils.
    So who knows?
    Last edited by RothwellAudio; 08-02-2018 at 15:28.

  7. #7
    Join Date: Jul 2016

    Location: West Wales

    Posts: 143
    I'm Jonathan.

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    My Zyx cartridge states the same (>100) and it sounds a lot better at 220 ohms both with an Edwards Audio MC3 and Whest PS 30 RDT SE. There must be a reason the manufacturer sets a minimum so I have never tried it at a lower setting.

  8. #8
    Join Date: Feb 2016

    Location: Melksham, Wiltshire

    Posts: 726
    I'm Peter.

    Default

    Quote Originally Posted by RothwellAudio View Post
    Yes, > 100 ohms means greater than 100 ohms, so it only sets a lower limit. Most LOMC cartridges are specified that way with only a lower limit. In theory anything above the quoted figure should be fine and make no difference to the sound but in practice some people find a subtle improvement with a higher figure than the minimum. Some people claim that one particular load value makes the cartridge sing and everything else sounds terrible but I suspect they're exaggerating.

    The usual explanation is that the inductance of the cartridge's coils produces a peak in the frequency response and the load impedance tames the peak. However, doing the maths with some typical cartridge specs makes this explanation less than convincing.
    Another possibility is that lower load impedances draw more current from the cartridge and that current flowing through the coils produces a back EMF which damps the motion of the coils. It's the same principle as a power amp with a low output impedance damping the coils of a loudspeaker. However, once again the maths doesn't prove this theory entirely convincingly because the damping effect of the stylus suspension swamps the effect of the current in the coils.
    Sp who knows?
    So......

    I think I’m still missing the point (Sorry I’m in dumb mode) but I do sort of understand you reply.

    Can I give you two examples.

    1. My main cartridge (Benz Wood SL) output impedance of 12 Ohms, this times ten = 120 Ohms. I don’t have a 120 Ohm setting on the Whest, so it’s either 100 or 220 Ohms. (Gain is not an issue, I understand that bit). So why does it sound better at 220 Ohms when on paper, that’s more than is required.!!!

    2. My Second cartridge is the (Denon 103 Pro) output impedance of 38 Ohms. This times 10 = 380 Ohms. Again there is no setting for 380 ohms, so it’s either 220 Ohms or 470 Ohms. But to my ears, sounds better at 220 Ohms, Which it exactly the opposite scenario of the Benz. Again, on paper, this is Less than required.

    Perhaps the numbers are all meaningless and it’s a Use Your Ears thing !!

    Sorry but just trying to get my head round this !!!! as I’m planning in the future to get a decent Cartridge, “ Perhaps the Dynavector DTR XV-1s” or is the 4K asking price wasted if I don’t know or understand the optimal loading point.

    Thanks in advance.




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  9. #9
    RothwellAudio Guest

    Default

    Quote Originally Posted by Boyse6748 View Post
    Sorry but just trying to get my head round this !!!! as I’m planning in the future to get a decent Cartridge, “ Perhaps the Dynavector DTR XV-1s” or is the 4K asking price wasted if I don’t know or understand the optimal loading point.
    Show me somebody does know or understand the optimal loading point. If there was one, it would be logical for the manufacturer to know what it is and specify it - but they don't. If I was being cynical I might say that Brand X know their top-flight cartridge sounds best with a load of 137.9 ohms but won't say so because they know there are no phonostages which offer that load, so it's safer to say ">100 ohms" instead and that way they won't lose any sales.
    More likely, it doesn't matter all that much and anything above a certain figure will be fine.

    Anyway, don't get too hung-up on the x10 thing - it's only a rough guide. I guess it originates from the need to define a minimum load impedance for an acceptable signal loss. Take 1dB of signal loss as an arbitrary figure and you end up with the x10 "rule".

    I have no explanation for your empirical findings, sorry. With the Denon, how much of a difference is there between the 220 and 470 ohm settings? How sure are you that you have the same listening levels when making comparisons? Is the difference enough to worry about?

  10. #10
    Join Date: Feb 2016

    Location: Melksham, Wiltshire

    Posts: 726
    I'm Peter.

    Default

    Thank you Andrew, wise words indeed.

    You have convinced me....... just Sit, listen and enjoy. The different loadings are so minute to the overall sound..... Perhaps it’s just not worth losing sleep about!

    Peter .


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