Stopping EMF between Naim Units

Please excuse my ignorance here, but as I understand it the stack position device rules (e.g. brain and brawn) are around keeping big transformers away from devices without transformers (e.g. Pre-amps) due to the EMF produced by the transformers. So presumably the metal boxes they are enclosed in is not enough to eliminate escaping EMF

I may be over simplifying this, and sorry if I get lost by the detailed responses I may get back, but if this is a large problem and you cannot physically easily separate your Naim devices, can you simply add say a metal sheet underneath each unit, and if so how thick would it have to be?

I bet @Simon-in-Suffolk has a good answer :slight_smile:

I’ve played around with this, I had a sheet of mu-metal that I cut to fit to fully cover the Supernait shelf that has NDX below & used that connected to earth/ground & also unconnected. TBH I could not detect any audible change or measurement change of any kind with the screen in place or not.

My units sit on 18mm thick shelves & there is aprx 44mm distance between top of one unit & the bottom of the other. OK it’s not as wide a distance as we get with Fraim, but based on what I’ve experimented with, I’m not changing anything.
However a lot of people firmly believe in brain & power separation so I suspect there is some truth in the need for separation, it’s just that I couldn’t hear it with my setup. Maybe the inactive traffo in my NDX is part of that.

I found the same subject on www & it showed …
As long as the magnetics are closed loop toroids and not saturated, they won’t leak much field.

Thanks Mike. Nice to hear that someone has considered it. EMF apparantly travels through wood and glass quite well, hence my consideration for my 10mm shelves. Also mine are stacked on double width shelves, which only leaves about 30mm gap between some of them, so if this worked, I could perhaps create a vertical panel to help here. Lets see what other shave found

Naim’s PS transformers are enclosed in metallic boxes that act like a Faraday cage, which should be enough to isolate the transformer.

The magnetic field around a toroidal transformer is limited.

I could certainly hear the effect of a 500’s power supply on a 552 head unit, or rather the improvement when I moved the 552 up a shelf and further from it and the 555ps below the 500ps.

Hi @Thomas that was my thinking, but then lots of people on this forum swear by the importance of stack placement, hence raising as a topic.

The field in any event drops off quite rapidly with distance due to the inverse square law, which applies to EMF radiation.

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Thanks, in which case it shouldn’t matter too much. So perhaps it’s all perceived SQ change that people find when they move their boxes around

Indeed, your question makes sense.

But, honestly I have no idea.

Both the NAC and its power supply are enclosed in Faraday cages.

The power supply’s toroidal transformer produces a VERY limited magnetic field.

The obvious conclusion should be: placing the power supply in a different Fraim shouldn’t make the slightest difference.

Apparently, it makes one.

So the question remains.

Why placing the PS elsewhere makes a difference?
From where does the leakage come from?

I’d bet my money on the cables, the Burndies… :wink:

The answer should be easy to find.
Magnetic fields are easy to measure :

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The caveat though being that toroids suddenly behave much worse than EI if subject to DC offset. If your mains isn’t great and the offset is enough to make a toroid hum, they suddenly saturate and produce more EMI than an EI. Something EI are very resilient to. Toroids are very Jekyll and Hyde in this respect.

In the design for high end components, most EI transformers employ sufficient shielding. Yet toroids tend not to and rely heavily on perfect mains. Which, the forum reveals is quite difficult for some regions.

FWIW, there used to be a statement on the original Fraim brochure indicating 13cm between shelves provided the required distance to ensure sufficient EMI dropoff.

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OK, so the standard metal case might not be adequate if you have dirty mains (DC Offset etc). This might explain why some people hear a difference, and others do not.

Does that mean if you have mains issues, adding a metal sheet above or below your Power Supplies may help SQ

Really, 13 cm ? :flushed:

That would mean the PS case isn’t a Faraday cage and the the transformer produces an enormous magnetic field, considering how fast it drops off with distance.

I very much doubt the magnetic field produced by the toroidal transformer passes the case barrier, or even has any significant effect at a distance of 5-6 cm from the transformer itself (within the case).

But again, that is something really easy to measure.

There already is a metal sheet between them: the case. If that isn’t doing the job, then short of a lead sheet, physical distance would be the way to go.

13cm between shelves is something like 4cm between units. Anyway, Naim’s words not mine and they aren’t published anymore.

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Faraday cages don’t work well on constant non fluctuating fields.

From what I learnt, if the Faraday cage is an actual Faraday cage then the magnetic field within the cage is barely, if not, measurable from the outside. And vice versa.

In the context of a toroidal transformer this is even more true.
A toroidal tranformer’s very limited magnetic field leaking from a Faraday cage… sounds quite unlikely.

To put things into perspective, the gigantic NAC S1’s toroidal transformer isn’t far from the very sensible circuitry… same thing for the NAP S1 (not to mention the NDX2, SuperNait 3, NAP250, etc.).

So, to come back to @GadgetMan question ; A lot of members experience “a better” when placing the NAC’s PS away from its head.

I bet on the cables (the burndies carry a lot of current).

You bet on a faulty Faraday cage.

We really should borrow one those testers and clear things out :smiley:
That would be really interesting :nerd_face:

They seem to be only £20 on amazon. I’d be happy to have a go, but it might be better in the hands of someone with more electronics knowledge. Also better with someone with bigger PS’s than me possibly.

If they are any good, then it may be something more of us can get

I wouldn’t buy a cheap tester.

I’ve been wondering about the same thing for quite a while…

I’ll probably borrow one of those testers one day, a good one providing the necessary precision, and publish my findings.

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Nice one @thomas that would be very helpful to a lot of people

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You may have been misinformed here. Faraday cages are very effective at blocking RFI interference and transient EMI like static discharges. They won’t, for example, block the flux field from a magnet. It is stable, more or less constant in terms of intensity with zero frequency. Ditto for flux on a transformer such as a saturated toroid. To block that, materials based magnetic shielding is required.

I don’t believe I’ve ever said or implied that. I just don’t think the case does what you think it does.