SMPS and grounding

[lmitche]

5 minutes ago, austinpop said:

Gaah - turns out the screw terminals I ordered from Amazon are crap! About 90% don't want to tighten properly.

 

Avoid this POS, please: https://www.amazon.com/gp/product/B01ER6QWAY

 

I will try another brand...

Please let us know what you choose.

[lmitche]

John, WOW what a great explanation of the cause of the mysterious SQ changes we hear so frequently.   I even get it.  Many thanks!

 

Larry

[lmitche]

The purpose of the new Netgear switch, properly grounded, is filtering low and high impedance leakage currents from your music PC.

[lmitche]

I should have written that the new Netgear switch, properly grounded, is filtering low and high impedance leakage currents created by your SMPS and the rest of your network from your music PC.

 

I believe that John wrote that the ground strap on the switch is irrelevant.

[lmitche]

33 minutes ago, rickca said:

Is BJC Cat 6A OK to use?  It's supposed to have a floating shield.

I have lots of belden based bjc cat 6a cables and having re-terminated several, know that the cable is shielded but floating on both ends.

 

The internal structure of this cable is really something. I have no idea how they can cheaply manufacture something with this complexity.

[lmitche]

Yes, unconnected shield on bjc cat 6a cables.

[lmitche]

12 minutes ago, thyname said:

And once we get it at hand, how do we check which version?

There is a label with the version number on the bottom of the device.

[lmitche]

2 hours ago, BigGuy said:

IIRC, there was a much earlier post about the need to have the two ends of the shield connected to each other by an insulated wire otherwise the unconnected shield is just metallic sheathing.  Or does it serve a purpose even unconnected?

My post was meant to share my experience that the bjc 6a cable shields endpoints are not connected to the ethernet plugs.

 

I have no experience with insulated wire connecting shield endpoints. Likewise you will have to ask Belden about the advantages of the metal shield on their cables. I would be guessing.

[lmitche]

25 minutes ago, Johnseye said:

 

 

 

It sounds like cat 6a is ok to use, and may even be better because of the shielding as long as the shield is floating.  Is this accurate?

Oh boy, I guess we are having reading comprehension issues today, LOL!

[lmitche]

1 hour ago, ted_b said:

As I build a few LT3045s in series (for example, 9v ps into 7.5V, out into 6v in, for ISO Regen) I am contemplating using this same wire for the same reasons (no strands, lt3045s less than an inch apart, etc).  Is this right thinking or is the solid copper 14awg a poorer choice for this kind of application than, say, the star quad wires used on the rest of the project (for female and male dc cables or plugs, for example).  It's way easier, and assuming I sort of breadboard them with a plastic base I assume they won't bend, etc.  Any opinions?

Having built three of these I much prefer the solid core wiring on the left.  This makes the whole assembly more solid which I useful when plugging power cords in and out which is often literally a stretch.  I also used plastic pcb board standoffs to make a multi layer assembly for both two and four boards assemblies.  Again this solidifies things further.

 

Of course a box for one or more of these makes the most sense, however I'm stilling discovering the optimal placements, so when found I'll think more about packaging for the long haul.

[lmitche]

40 minutes ago, Forehaven said:

I sent Ted the solid core, from my Bonsai work, it's 14g annealed.  Does the annealing process Larry make this particular solid core Cu less than ideal?

LOL, I have no idea.

[lmitche]

5 minutes ago, JohnSwenson said:

Your Dac

This grounding is only for SMPS. If your DAC has an SMPS then some form of grounding will probably be good. Since it supports 120 or 240 and there is no voltage selector switch it is PRPOBABLY an SMPS inside, so grounding is probably a good thing.

 

Interestingly there is a ground select switch on the back, setting this to "chassis" will probably do the appropriate grounding without having to worry about anything else. Try the ground switch both ways and see what sounds the best. No need to do any other external grounding.

 

John S.

Naim gear is always star grounded through the DIN connectors, hence the weird cable routing through preamps . . . etc.

[lmitche]

19 hours ago, JohnSwenson said:

Hi guys, I was going to post on this, but these recent posts are just what I have wanting to talk about.

 

I've been doing a bunch of measurements on both Ethernet and USB cables. This has to do with leakage being common mode, radiation from cables may be very different than commonly assumed.

 

Ethernet:  leakage current is common mode, the same on both data wires.

    UTP:  No shield, common mode leakage it radiated very well from the twisted pair. Twisted pair makes no difference, both wires have   the same thing

  STP: Shielded cable, metal connectors at each end, shield connected from box to box. Leakage goes right through shield, the shield makes a great antenna radiating the leakage.

 STP: shield is not connected to either end. Provides a little bit of attenuation of radiation due to leakage current.

 STP: JSSG, a single wire connect both ends of shield, ends of shield NOT connected to boxes. Since the shield is not connect to the boxes leakage cannot flow through shield. The wire connecting both ends of the shield does a very good job of blocking the radiation from the leakage current.

 

So for a system that DOES have leakage going through the Ethernet cable, all but the last will be radiating low frequency noise from the cable which can be picked up by normal audio cables and devices.

 

USB cables have a similar situation

 

Normal cable: shield connected at both ends, leakage flows through shield, radiating leakage.

Un-shielded cable. Leakage flows through ground wire and also VBUS and data. Due to geometry of cable and how leakage gets into data pair, does not radiate as good as UTP. less radiation that regular cable. May be why some people like un-shielded cables.

Un-shielded just data pair. With no ground wire and VBUS wire, leakage through just data pair is quite a bit less, producing significantly less radiation than normal cable.

normal cable, but JSSG, shield NOT connected between boxes. The JSSG shield blocks a very large amount of the radiation from leakage. Still has full ground, VBUS and data wires, without leakage radiation.

 

This leads me to think that a lot of systems are actually picking up noise due to radiation from leakage flowing through the Ethernet and USB cables. This may actually be why some people like some weird configurations of cables.

 

Note that this has absolutely NOTHING to due with the actual data going through the cable, it is just due to leakage from power supplies going between between boxes through the digital cables.

 

Note that this is from leakage, if you stop the leakage from flowing through the cable, all this cable stuff above makes no difference.

 

Just some more food for thought.

 

John S.

 

Hi John, 

 

Many thanks for sharing this information on cable shielding. Two questions please:

 

In your parlance we have shield connected, shield unconnected and no shield.

Does adding a disconnected shield layer with the "jssg" ground shield return wire accomplish the same reduction in radiated rfi emi in all three cases?  I am thinking of adding tinned copper sleeving with an insulated 14 awg stranded and insulated wire on the outside.

 

https://www.amazon.com/Tinned-Copper-Metal-Braided-Sleeving/dp/B01BIBQESG

 

I appreciate that with the shield connected cable adding the sleeving will not stop any leakage current flow through the existing connected shield.  Nevertheless will radiation be reduced?

 

The additional tinned copper sleeving may be a cheap and simple way to accomplish the benefits of the JSSG design for existing ethernet and usb cables.

 

Thanks again,

 

Larry

 

P.s. I am very much enjoying the ground shunt trick on the two Sigma 11 power supplies powering my USB HDD enclosure and repurposed Netgear switch. Thank you very much.

[lmitche]

17 minutes ago, JohnSwenson said:

Yes a separate shield around the existing cable, when properly connected with a wire end to end will block a large amount of the emissions from the existing cable.

 

John S.

Thanks John,

 

I am curious, what is the theory of operation for the end to end wire? Does it make the cable a poor antenna? 

 

Adding the tinned copper sleeving and wire to the Lush USB cable this afternoon had a noticably positive impact. I'll do the same to my ethernet and usb 3.1 cables later in the week.

[lmitche]

30 minutes ago, gstew said:

Larry,

 

See here:

 

Greg in Mississippi

 

Thanks Greg,  sorry forgot that one, LOL.  John you are amazing!

[lmitche]

9 minutes ago, tboooe said:

Guys a question.  I am trying to figure out if its worth trying this grounding technique on my power cables...I use some Synergistic Research power cords which have "active shielding" that requires a SMPS.  Is it possible for SMPS leakage to go through the AC power cord, into my equipment and eventually into the rest of my system?

 

Here is the explanation of active shielding:

Our first experiments with Active Shielding began early in 1996, and involved the placement of batteries in a static circuit, with the positive annode of the battery tied to a conductor running the length of a cable, and the negative annode of the battery tied to the shield. These initial prototypes subjectively improved performance in the high frequencies. However, they also increased the noise floor (especially on long runs), with the positive conductor running the length of the cable (and not being terminated to signal or ground) thus acting like an antenna picking up RFI and EMI.

We then experimented with closed circuits, where the shield carried a DC current, with a buffer circuit between shield and ground and separate conductors carrying the ground signal. This closed circuit design not only improved subjective performance, but also made our cables measureably quieter, thus improving detail with greater frequency extension from top to bottom. Since a closed circuit draws current, we could no longer use batteries, as this would drain a battery in a matter of hours.

Given the ease and low cost of implementation, why not give it a try? I suspect you will be postively surprised.

[lmitche]

30 minutes ago, tboooe said:

Holy smokes.  Just measured the output from the Synergistic Research SMPS powering the active shielding of my power cables and its 35V!  Not what I was expecting.  

AC or DC?

[lmitche]

3 minutes ago, austinpop said:

@Superdad

 

Once you get Meanwell to start internally grounding their SMPSes for you, will you have them change their name to DoWell?

How about GroundsWell?

[lmitche]

54 minutes ago, austinpop said:

 

Jealous I didn't think of that.   It's brilliant!  

BeWell Rajiv.

[lmitche]

3 hours ago, hopkins said:

Getting back to the use of a Netgear switch and the choice of RJ45 cables: would it make sense to  wrap cables with RFI shielding tape (ex: copper tape)  UTP cables going to and out of the switch, or is this complete overkill ? In general, does it make sense to use shielding tape on any type of cable around an audio system ?

Shielding has had a big impact on DC power and digital signal carrying cables here.

[lmitche]

9 hours ago, Em2016 said:

 

Using copper tape together with John's shielding technique?

 

Or using existing shielded cables with John's shielding technique?

 

I've never tried copper tape, but tinned copper sleeving has a huge impact applied in the so called jssg fashion.

[lmitche]

Just type tinned copper sleeving into Amazon. You will find it.

[lmitche]

17 hours ago, JohnSwenson said:

Hi Luis,

 

the JSSG is a way to make cable shielding work at low frequencies. If you have a cable with a shield and don't use JSSG it will shield at high frequencies , but not low frequencies. ALL audio frequencies are considered low in this regard. Leakage current from SMPS are also considered low frequency.  Shielding can be keeping stuff from getting in and also for preventing stuff from coming out.

 

In order to figure out what needs to be properly shielded think about what the cable is for and what flowing through it. For example:

 

audio interconnect: high impedance analog signals, JSSG keeps the cable from picking up low frequency external signals, this is usually a very good thing for audio.

 

Ethernet cable: probably not too much affected by picking up low frequency signal, BUT leakage from SMPS powered LAN equipment can be radiated from the cable. JSSG prevents that from happening. Another way to deal with this is to go with the special switch that shunts SMPS leakage, so downstream of the switch there is no leakage on the Ethernet cable so the JSSG is not needed.

 

USB cable: can also radiate leakage current. If there is SMPS leakage going through the cable then JSSG will prevent that from radiating. If the USB source is powered from a LPS-1.2 there will be no leakage into the device from the power supply, but there still can still be leakage coming in over the Ethernet port. Using the special switch approach blocks that. In that case (no leakage going into device from PS and no leakage coming in from any other input) you do not need JSSG on USB cable. If any of that is violated then JSSG on USB will help.

 

So for any set of connected devices run this through the stsem, if the PS powering the device does not have leakage, and all inputs do not have leakage, you do not need JSSG on an output cable unless that cable is carrying a low level sensitive signal (like analog audio signals)

 

When "walking the tree" applying the above from device to device, the special switch (with appropriate power supply) blocks up stream leakage so you do not need to traverse further up stream.

 

Does this help?

 

John S.

 

 

 

 

Hi John,

 

Despite use of the Netgear switch, two lps1s, and an ISO Regen there is still a benefit from jssg here for both usb cables, dc cables and ethernet cables.  Any idea what is going on?

 

Thanks,

 

Larry

[lmitche]

23 minutes ago, lvc10000 said:

Thanks Luis for the recap as I had missed the JSSG. And thanks to John for sharing. Will look into it for my Sonore DC + mini USB stub cables of my LPS-1 & Rendu. Awesome stuff.

 

I was just about to try to slip on some steel braided shielding over my preferred sata cables (ordered last week) to check it out but now am thinking about adding a wire linking both ends of the shielding under the heat wrapping to JSSG it.

Worth a try ?

Yes worth a try. You could try it both ways as well, with and without the loop wire.