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PostPosted: Sun Jul 01, 2018 8:25 am 
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I'm moving these here from my PoE DC thread -
Using a very sensitive ELF EMI detector - one with sensitivity down to 0.1mG (+/-5%) and measures in the ELF EMI range (30Hz-300Hz) where the JSSG is supposed to be extremely effective. And as stated above JS claims that having no JSSG loop on a shield makes it almost totally ineffective.
If you get one of these testers - or even another tester (please porvide sensitivty and frequency range then) - feel free to post your measurements here. Would like to see some on the Meanwell SMPS's.

Here is the tester - note the detection sensor is at the top only:
Attachment:
s-l1600 (12).jpg
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My nifty EMI detector arrived - this one I bought because it had a narrow 30Hz to 300Hz range. So the perfect ultra low freq AC related EMI hunter.

And here is what I found:

Still think SMPS's are benignant little boxes - placed right next to your sensitive digital gear (with femto clocks)!
Here is the SMPS from my Dell laptop:
Attachment:
Dell SMPS.jpg
Dell SMPS.jpg [ 199.01 KiB | Viewed 1777 times ]

148 Milli-Gauss - the device lights up Red and sounds an alarm at 5mG!

And well hunting around my system - I found these culprits! Never would have expected this from Synergistic Research - the Tesla and Galileo MPC's
at over 1485mG - in fact at a certain spot I hit OL (overlimit). Must be SMPS's for sure!
Attachment:
MPC L1.JPG
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Attachment:
MPC.jpg
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I originally posted this as 76mG, misread the reading - there was no decimal point! Actual reading 768mG!
Attachment:
LT1083 LPS.JPG
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The DC-30W R-Core:
Attachment:
DC-30W LPS.JPG
DC-30W LPS.JPG [ 204.67 KiB | Viewed 1777 times ]


Same misreading - actually 789mG! And I had to hunt around the case to find the highest reading. All the power supplies were measured powered up and feeding current.

More measurements...


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PostPosted: Sun Jul 01, 2018 8:34 am 
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Moving to my iCore 7 PC server with a high PSRR fanless SeaSonic SMPS - even with the case off - not too bad:
Right at the side of the SeaSonic SMPS (with the music playing and server running) - 3.5mG Below the alarm threshold!
Attachment:
PC Seasonic.JPG
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At the back of the PC right at the AC inlet - 19mG
Attachment:
PC at the AC inlet.JPG
PC at the AC inlet.JPG [ 334.34 KiB | Viewed 1775 times ]


So really well designed PC SMPS's are not too bad - not like those SMPS bricks/wall warts!

At the USB hub virtually 0
That was good to know as it's in somewhat closer proximity to the PC.:
Attachment:
USB hub.JPG
USB hub.JPG [ 388.77 KiB | Viewed 1775 times ]


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PostPosted: Sun Jul 01, 2018 8:38 am 
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But here was another clue as to where some MuMetal is needed - at the back of my amp.

Where the Speaker terminals are near the AC inlet.

First the reading on the non-AC side top and bottom of the right side:
Attachment:
Top R Spk.jpg
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Attachment:
Bottom R Spk.jpg
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Now the left AC side:
Attachment:
Top L Spk.JPG
Top L Spk.JPG [ 204.04 KiB | Viewed 1774 times ]

Attachment:
Bottom L Spk.JPG
Bottom L Spk.JPG [ 417.89 KiB | Viewed 1774 times ]


Ah! The bottom of the left speaker terminals with a level much higher then the right side. In fact all these levels are too high. Not good.

But with MuMetal - the level is way lower. So all these terminals will get the MM treatment -with a double layer at the bottom of the Left terminal.
Attachment:
Bottom L Spk w MuMetal.JPG
Bottom L Spk w MuMetal.JPG [ 348.92 KiB | Viewed 1774 times ]

Fun stuff!

Cheers


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PostPosted: Sun Jul 01, 2018 8:47 am 
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Some more pretty shocking measurements on power supplies:
I decided to do a more thorough scan of the ELF EMI on these power supplies and it was worse then I originally thought.

First the Dell SMPS, now measuring from the bottom:
Attachment:
DELL SMPS2.jpg
DELL SMPS2.jpg [ 239.9 KiB | Viewed 1771 times ]


578mG!

And on the DC-30W - ugg!
Attachment:
DC30Wfront.jpg
DC30Wfront.jpg [ 198.27 KiB | Viewed 1771 times ]

756mG at the direct front!! Fortunately this very strong field does not radiate at this level on the top and bottom - nor to the sides. But what about the back?
Attachment:
DC30Wbacktop.jpg
DC30Wbacktop.jpg [ 203.26 KiB | Viewed 1771 times ]

A much better 48mG at the top back of the case.
What about the AC socket input and most importantly the DC output?
Attachment:
DC30Wback DC.jpg
DC30Wback DC.jpg [ 218.73 KiB | Viewed 1771 times ]

5.6mG at the DC head. Just above the alarm threshold, and far better then the 756mG at the front.

One note the EMI field is very sensitive to movement. The levels jump on even small relative motion. So I was very careful to stabilize the tester and wait a bit to take the photo. This is probably why vibration isolation is so important for audio. I imagine even micro movements caused by all sorts of things excite all the various electro-magnetic effects inside our gear - even outside!

I would certainly would not want to place any audio gear at the front - or point a LPS at them.

Cheers!


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PostPosted: Sun Jul 01, 2018 8:54 am 
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As for the extension of the field on the DC30W to the front:
Attachment:
DC30W2inchesfront.jpg
DC30W2inchesfront.jpg [ 208.68 KiB | Viewed 1770 times ]


Here the inverse square law is our friend. At 2 inches the ELF field drops to 69mG

At 5 inches...
Attachment:
DC30W 5inches front.jpg
DC30W 5inches front.jpg [ 216.09 KiB | Viewed 1770 times ]

Still pretty high at 12mG.

Distance here of at least a foot or more is needed to drop the levels sufficiently.


Here is some other gear I tested.
What about PC CPU's - long thought to be huge EMI emitters
My fanless Kodlix - 0!
Attachment:
Kodlix.jpg
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What about an iCore5 running music files?
Attachment:
iCore5 PC music server CPU.JPG
iCore5 PC music server CPU.JPG [ 135.25 KiB | Viewed 1770 times ]

Actually no much 1.8mG.

Latest gen Seagate 2TB portable USB 3.0 HDD
Attachment:
Seagat 1TB USB 3.0 HDD.jpg
Seagat 1TB USB 3.0 HDD.jpg [ 324.93 KiB | Viewed 1770 times ]

7.8mG - not bad considering it has a motor with magnets and is spinning.


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PostPosted: Sun Jul 01, 2018 8:58 am 
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My AD1865 DAC with an R-Core:

At the front the worst readings:
Attachment:
AD1865DAC front.jpg
AD1865DAC front.jpg [ 206.15 KiB | Viewed 1769 times ]


57mG - not as bad as the DC-30W

How about at the critical rear analog outputs?
Attachment:
AD1865DAC back output.jpg
AD1865DAC back output.jpg [ 373.26 KiB | Viewed 1769 times ]

Nice 0!

But at the AC socket:
Attachment:
AC DAC.JPG
AC DAC.JPG [ 359.35 KiB | Viewed 1769 times ]

19mG not good.

I'm thinking of putting in Mu Metal shielding in both my DACs between the R-cores and the digital circuits - maybe a four layer shield.


Attachments:
AC DAC.JPG
AC DAC.JPG [ 359.35 KiB | Viewed 1769 times ]
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PostPosted: Sun Jul 01, 2018 9:00 am 
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Ok last one - this kind of blew me away.

On my speaker cables in the main system:
Attachment:
TQUB no music.JPG
TQUB no music.JPG [ 396.61 KiB | Viewed 1768 times ]

Attachment:
TQUBno music2.JPG
TQUBno music2.JPG [ 390.31 KiB | Viewed 1768 times ]


No music playing - but amp turned on and in mute - 0mG

But when the music was playing - look at the ELF field jump!
Attachment:
TQUB music2.JPG
TQUB music2.JPG [ 399.31 KiB | Viewed 1768 times ]

Attachment:
TQUB music.JPG
TQUB music.JPG [ 359.92 KiB | Viewed 1768 times ]

29mG and it would vacillate with the music dynamics!

I'd keep my speaker cables far from my digital gear.
Fortunately my amp sits on the vibration cones (can't speak highly enough of these carbon fiber BDC racing cones, pits and pucks!)
and my speaker cables are many feet from my digital gear. But I see in a lot of rack type situations the speaker cables in fairly close proximity to the digital gear.

Cheers!


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PostPosted: Wed Jul 11, 2018 7:38 am 
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Hi
Nice post. Where did you get that meter and please fill us in {not so tech guys} what and how we can better our system for this
Can a pure copper shield or tin platted copper shield Or what type of stuff are you talking about where can you get it
And does it have to be braided
can you get sheets of it and wrap it around certain areas
Please show me some links to where we can buy the meter and the stuff your using to block the unwanted fields


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PostPosted: Wed Jul 11, 2018 7:51 am 
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carlthess50 wrote:
Hi
Nice post. Where did you get that meter and please fill us in {not so tech guys} what and how we can better our system for this
Can a pure copper shield or tin platted copper shield Or what type of stuff are you talking about where can you get it
And does it have to be braided
can you get sheets of it and wrap it around certain areas
Please show me some links to where we can buy the meter and the stuff your using to block the unwanted fields
Hi, sure here is the link to the tester:
https://www.ebay.com/itm/Meterk-EMF-Met ... 2749.l2649

Copper can work quite effectively, esp copper braid on wire - see this thread:
Does JSSG Really Work? Well here is an Actual Test
viewtopic.php?f=35&t=1469

Copper sheeting has to be thick to work. The best for ELF EMI is Mu Metal as shown above. Even very thin sheets work quite well. And of course can be doubled and tripled up.
https://www.ebay.com/itm/Ultraperm-80-M ... 1438.l2649

But as this thread was intended to show - distance is your best friend when it comes to keeping this kind of noise (as opposed to RFI) from negatively effecting your audio gear - especially sensitive digital gear. Simply rearranging your gear placement can go a long way to min this issue. And it's free.

Power supplies are a big culprit both LPS and SMPS.

And SMPS have other issues as well, like high impedance leakage.

Hear an audio engineer John Swenson explains:
Quote:
Leakage current, this comes from all AC powered power supplies, it travels through cables to other power supplies and back to the AC line. Ethernet devices wired with copper cables contain transformers, most people think that these block leakage, well yes and no. They DO block the low impedance leakage that most people measure when they talk about "leakage". But it turns out that SMPS power supplies generate a different type of leakage I call high impedance leakage, which goes right through these transformers. I've written in great detail about this in other posts. So what is bad about leakage? It travels through the ground plane of your devices, even all the way down to the DAC, and flows through the ground planes of the devices. This creates a noise on the ground plain with the same spectrum as the leakage, which is right in the middle of the audio range. The ground plane noise increases the phase noise of the clocks sitting on it, in particular the clock in your DAC. This added phase noise causes distortions in the audio signals coming out of the DAC. The cheap SMPS supplied with most consumer LAN equipment generates huge amounts of this leakage current.
Best to eliminate all SMPS's from your audio system.

Cheers!


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PostPosted: Tue Jul 17, 2018 8:43 am 
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Found some 3M EMI Absorber SB5020 in one of my many boxes of electronic stuff. So I thought why not give it test on that Dell SMPS and my ELF EMI tester.

Surprising it worked really well!
Attachment:
3M AB5020.JPG
3M AB5020.JPG [ 333.35 KiB | Viewed 1245 times ]

Dropped the 480mG down to 80mG an 83% reduction - better then MuMetal!

Will have to order some of this for my DAC PS shielding projects.
http://www.hillas.com/Categories/3M-EMI ... gIyTvD_BwE

Cheers!


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PostPosted: Fri Sep 07, 2018 8:49 pm 
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The link does not work


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PostPosted: Sat Sep 08, 2018 9:51 am 
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carlthess50 wrote:
The link does not work
Which link?


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PostPosted: Sat Sep 08, 2018 3:17 pm 
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Now it is working. Lol


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