Tesla meters - has anyone used one?

yespsb

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I want to test a few old direct drive turntables from the 80s for motor EMI leakage before deciding on which one to restore.
Has anyone used one in relation to testing hi-fi equipment? I would welcome your feedback.
Thanks in advance Paul
 

Beobloke

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You’ve not been reading Korf Audio’s blog have you?!

What decks are they?
 

yespsb

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You’ve not been reading Korf Audio’s blog have you?!

What decks are they?
Now you come to mention it maybe I have 😉
There's quite a few to inspect, all Japanese, too many to list. The potential EMI leakage will definitely have a say in what cartridge I choose, definitely no moving iron.
 

John (big)

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Now you come to mention it maybe I have 😉
There's quite a few to inspect, all Japanese, too many to list. The potential EMI leakage will definitely have a say in what cartridge I choose, definitely no moving iron.
Why no moving iron ?...
 

Jazid

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Korf audio reckon the magnetic flux leakage from direct drives reduces transparency, although they do not back this up with their usual suite of relevant measurements, so conjecture from the engineers. If you subscribe to this position then apparently whatever is your fave Jap d/d is a piece of shite, and impossible to improve. What to do?

Thusly I imagine that Korf Audio have a solution, not unlike their solution to the problem of no good tonearms ever having yet been built - build a perfect one like nobody could do before! Simple. Call me psychic but I reckon their yet to be announced belt drive will have Voyd like qualities of multiple motors on different, maybe multiple phases, a massive platter and many graphs proving reduction in resonance &c.
 
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yespsb

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Korf audio reckon the magnetic flux leakage from direct drives reduces transparency, although they do not back this up with their usual suite of relevant measurements, so conjecture from the engineers. If you subscribe to this position then apparently whatever is your fave Jap d/d is a piece of shite, and impossible to improve. What to do?

Thusly I imagine that Korf Audio have a solution, not unlike their solution to the problem of no good tonearms ever having yet been built - build a perfect one like nobody could do before! Simple. Call me psychic but I reckon their yet to be announced belt drive will have Voyd like qualities of multiple motors on different, maybe multiple phases, a massive platter and many graphs proving reduction in resonance &c.
Can I swap psychic for cynic ? 🙂
I understand your tongue in cheek reply and I also understand that EMI is something to be taken into account which is why I am minded to put AK's theory to the test.
Fortunately I am not in a hurry so I will keep plugging away and when I finally get my hands on a decent Tesla meter I will report back with what I find. There's no rest for my curious mind 😊
 

John (big)

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According to AK (and I believe him on this) moving iron are most susceptible to EMI, then moving coil, then moving magnetic.
Reality is not always the same as theory or experiment. I live in RFI/EMI central on top of a hill surrounded by 2 airports a large number of phone masts & communication transmitters on top of buildings in Ealing Broadway sufficient to charge an in-line capacitor if a system case is grounded/earthed. I do have 100 clip on ferrites on TV, digital & power leads none on phono leads.
There has never been a problem with my 4 Cartridgeman moving iron cartridge's from Musicmaker' 1)2) & 3) to currently a Musicmaster MI on a Hadcock 242 Silver plus, grounded at the Croft phono stage, 35 + years ago I had a Dynavector HOMC 10 x 5 on an SME arm that picked up passing mini cabs though on the same arm a Shure V15 III MM had not.

I have never read on a forum of a Cartridgeman, Grado or Soundsmith MI having a problem with EMI, further I have checked the internet with regard to Decca & london Decca which have an accepted theoretical chance of a problem with EMI which does not appear to exist in reality.
Moving iron cartridges are essentially immune to capacitance only really resistance needing somewhat less than the standard 47k. Joe Grado who held the patent on moving coils chose to make moving iron cartridges since they have the lowest tip mass & therefore responding with lightening speed.

I have no vested interest in your choice of cartridge . It would be a shame however to be so dogmatic on the choice of cartridge or any component on the written word of another, have a listen you may be surprised. An aside I use a much lauded Croft phono stage, sadly no longer to be made, apparently Croft products do not measure well but sound sublime as does my Musicmaster.
 
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yespsb

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Reality is not always the same as theory or experiment. I live in RFI/EMI central on top of a hill surrounded by 2 airports a large number of phone masts & communication transmitters on top of buildings in Ealing Broadway sufficient to charge an in-line capacitor if a system case is grounded/earthed. I do have 100 clip on ferrites on TV, digital & power leads none on phono leads.
There has never been a problem with my 4 Cartridgeman moving iron cartridge's from Musicmaker' 1)2) & 3) to currently a Musicmaster MI on a Hadcock 242 Silver plus, grounded at the Croft phono stage, 35 + years ago I had a Dynavector HOMC 10 x 5 on an SME arm that picked up passing mini cabs though on the same arm a Shure V15 III MM had not.

I have never read on a forum of a Cartridgeman, Grado or Soundsmith MI having a problem with EMI, further I have checked the internet with regard to Decca & london Decca which have an accepted theoretical chance of a problem with EMI which does not appear to exist reality.
Moving iron cartridges are essentially immune to capacitance only really resistance needing somewhat less than the standard 47k. Joe Grado who held the patent on moving coils chose to make moving iron cartridges since they have the lowest tip mass & therefore responding with lightening speed.

I have no vested interest in your choice of cartridge . It would be a shame however to be so dogmatic on the choice of cartridge or any component on the written word of another, have a listen you may be surprised. An aside I use a much lauded Croft phono stage, sadly no longer to be made, apparently Croft products do not measure well but sound sublime as does my Musicmaster.
John I appreciate your comments, it's always good to get a different perspective and whilst I do lean towards listening to people like AK, nothing in my world is sacrosanct. That's why I removed the standard cone feet of my Rega Planar 8 and replaced with them with Isoacoustic feet which apparently makes me a Rega heretic but I don't care because it sounds better.
 

lazycat

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I'm surprised no one has suggested going straight to the experts.

 

Jazid

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Can I swap psychic for cynic ? 🙂
I understand your tongue in cheek reply and I also understand that EMI is something to be taken into account which is why I am minded to put AK's theory to the test.
Fortunately I am not in a hurry so I will keep plugging away and when I finally get my hands on a decent Tesla meter I will report back with what I find. There's no rest for my curious mind 😊
Yes, maybe. I would like to see evidence that stray magnetic flux causes loss of resolution, or definition, or indeed anything. I don't know better, but I will say that whoever put the development into direct drives in Japan, just when they were staggeringly rich and technically adept, with a huge internal market of rich audiophiles, must have had a bad hair day not to consider... umm... magnetic flux leakage. Really? Is there no simple way of measuring this, for people who crafted microchips for specific turntables, accommodated irregular vinyl pressings, eliminated noise in all corners of the analogue chain? Amazing that neither they nor a single broadcaster globally noticed the sound was a mess until the Korf blog a month ago? Really? Fair enough.
 

rabski

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Yes, maybe. I would like to see evidence that stray magnetic flux causes loss of resolution, or definition, or indeed anything. I don't know better, but I will say that whoever put the development into direct drives in Japan, just when they were staggeringly rich and technically adept, with a huge internal market of rich audiophiles, must have had a bad hair day not to consider... umm... magnetic flux leakage. Really? Is there no simple way of measuring this, for people who crafted microchips for specific turntables, accommodated irregular vinyl pressings, eliminated noise in all corners of the analogue chain? Amazing that neither they nor a single broadcaster globally noticed the sound was a mess until the Korf blog a month ago? Really? Fair enough.
I would have to add that inside any cartridge there is a comparatively strong magnetic field, concentrated in a small space. There has to be for it to work. My feeling is that it would take a relatively very strong external field to change the 'shape' of the field inside a cartridge, and a comparatively very weak field is going to have no discernable effect at all.
 

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