SMPS and grounding

[jventer]

10 minutes ago, jamesg11 said:

 

Not that there aren’t things to bother about - a tweaker friend, who I tuned into the js grounding idea & who ordered some of the plugs etc for such, was told by an electrical engineer that the tweak was ‘illegal’ in Oz.

From a fellow Aussie. We live in Nanny states.

Lots of hifi stuff are illegal here.

Wonder about the Groundhog?

[jamesg11]

Well, nanny state is not a concept honoured by me. But ... if our place burns down, the insurance companies will find plenty in my audio gear to justify a knock back on any claims ...

[sandyk]

35 minutes ago, jamesg11 said:

Not that there aren’t things to bother about - a tweaker friend, who I tuned into the js grounding idea & who ordered some of the plugs etc for such, was told by an electrical engineer that the tweak was ‘illegal’ in Oz.

 Hi James

 I am not surprised and have previously suggested as much.

 That's another reason I originally suggested the Silicon Chip solution of a 22nF 275VAC X2 capacitor to earth instead, perhaps with a 100 ohm (or a little lower value resistor) 0.25W resistor in parallel. Using a 0.25W resistor should prevent any possible (highly unlikely!) damage scenario to the owner as well, by going open circuit under an unusual fault condition.

As the leakage is from a high impedance source, even a 100 ohm resistor to earth would reduce the original half mains voltage reading to most likely under 100mV.

 Perhaps Silicon Chip were aware of the illegalities of a direct earth connection in Australia at least, and why they said to remove evidence of  the bolted on solution before requesting a service  ?

 

Regards

Alex

[One and a half]

1 hour ago, jamesg11 said:

Not that there aren’t things to bother about - a tweaker friend, who I tuned into the js grounding idea & who ordered some of the plugs etc for such, was told by an electrical engineer that the tweak was ‘illegal’ in Oz.

 

Go for it. <=24Vdc is Extra Low Voltage, do what you like, no licensing required.

[sandyk]

36 minutes ago, One and a half said:

 

Go for it. <=24Vdc is Extra Low Voltage, do what you like, no licensing required.

 

 Who is to know anyway ?

Despite my misgivings, I did connect a direct earth to the case of my Teac STB for an improved performance.

[Cornan]

8 hours ago, jamesg11 said:

Best to cover bases by getting a jssg usb cable.

 

Here is one from ATL Hi-Fi that might interest you. It is a proper starquad USB cable with dual floating shields with JSSG loop. My best USB cable up to date! ? It is quite valuable as well. Made on request only.

 

[sandyk]

I would have thought that the 2 parallel braided shields would already have a very low inductance, so I am surprised that connecting a single strand heavy gauge wire in parallel with both of them would make any noticeable difference.

 I will need to take John Swenson''s word on this. 

[charlesphoto]

4 hours ago, jamesg11 said:

Well, nanny state is not a concept honoured by me. But ... if our place burns down, the insurance companies will find plenty in my audio gear to justify a knock back on any claims ...

 

Might I suggest giving the adapter a quick wrap in electrical tape (or heat shrink). Looks “safer” that way though I’m sure fine without. 

[Cornan]

6 hours ago, sandyk said:

I would have thought that the 2 parallel braided shields would already have a very low inductance, so I am surprised that connecting a single strand heavy gauge wire in parallel with both of them would make any noticeable difference.

 I will need to take John Swenson''s word on this. 

 

To be honest I have'nt tried the dual floating shields without the JSSG loop on the USB cable. However, based on my experiences with Ethernet cable where I have tried a floating shield without JSSG loop the JSSG do make a difference for the better in my setup with only unshielded cables or JSSG through out.

[Johnseye]

17 hours ago, JohnSwenson said:

I have been looking into low frequency emissions from cables, both Ethernet and USB. The high frequency DATA from these cables is fairly well attenuated due to the twisted pair construction because the data is differential. Leakage is different because it is common mode (the same on both data wires). Because of this the twisted pair doesn't attenuate anything. UTP (un-shielded) radiates leakage like crazy.

 

A traditional shielded (STP) ethernet cable with both ends connected to ground doesn't help because the shield is ALSO part of the antenna (leakage current going through the shield). A traditional USB cable will also have the shield acting as a very good antenna for leakage. (maybe this is why some people like un-shielded USB cables?) A USB data pair may NOT be perfectly differential so the twisted pair may have some attenuation of radiated leakage. So a shieldless cable may be a benefit if there is leakage on the cable.

 

For both of these it seems like the JSSG technique (Shield not connected at either end except for a wire connecting both ends of the shield) would be of benefit. This would seem to provide attenuation of leakage radiation WITHOUT the shield carrying the leakage current and being part of the antenna.

 

Of course this is immaterial IF there is no leakage current going through the cable in the first place. So IF you can keep leakage out of the cables, a lot of these cable weirdnesses go out the window.

 

It would be interesting to see if getting rid of leakage in these cables means less cable sensitivities. 

 

John S.

 

On 11/2/2017 at 1:26 PM, Johnseye said:

 

 

 

In John's post linked above he states a connected shield will bypass the shunt.

 

In another post of John's linked above he said this: "If there is not such a path the only shielding that is going to happen is for high frequencies due to capacitance involved with the shield."

 

So, putting the two together the BlueJeans cat 6a with floating shield will not bypass the shunt.  Because it does have a floating shield it will still shield some high frequencies.

 

The only problem with this approach that I can see is that the shielding may cause internal crosstalk since alien crosstalk may not be an issue.  If it could be an issue, or there's a need to shield from external sources then this could be a better solution than UTP.

 

On 11/1/2017 at 6:22 PM, R1200CL said:

 

A floating shield is not recommended I think. The shield has to act like a Faraday Cage. Hence the JSSG.

 

 

 

On 11/1/2017 at 12:15 PM, 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?

 

This is exactly what I was getting at in my 11/1 post.  

[JohnSwenson]

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.

 

[Cornan]

21 minutes 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.

 

 

Epic sum-up John! This is one of many posts that end up in my personal collection of hifi wiki bookmarks. Great work! I really admire that you spend all this time explaining these things for us while you have other more important things to attend to. What can I say? You are worth a golden star for outstanding efforts in the audiophile world!  ?

[sandyk]

11 hours ago, jamesg11 said:

Well, nanny state is not a concept honoured by me. But ... if our place burns down, the insurance companies will find plenty in my audio gear to justify a knock back on any claims ...

 

We need to remember here, that 50HZ 240VAC is way more lethal than the half that voltage used by our American cousins.

Have you ever been on the end of a nasty 240V shock ? I have when I was younger, and couldn't even tell a worried child that I was O.K. for almost a minute.

240VAC  can even throw you across a room !

[mansr]

7 minutes ago, sandyk said:

Have you ever been on the end of a nasty 240V shock ?

How can I tell if they were nasty or just normal 240V shocks?

[Cornan]

9 minutes ago, sandyk said:

 

We need to remember here, that 50HZ 240VAC is way more lethal than the half that voltage used by our American cousins.

Have you ever been on the end of a nasty 240V shock ? I have when I was younger, and couldn't even tell a worried child that I was O.K. for almost a minute.

240VAC  can even throw you across a room !

 

What is the point to scare people instead of learning them how to protect them selves? Anyone reading CA will put themselves into possible dangers by using isolation transformers, ground isolators etc.  Why not educate them to protect them selves instead of cutting them off the opportunity to enjoy high end audio? A simple 2-pole RCD/GFCI at the output will do to protect them for possible dangers.

[Speed Racer]

8 minutes ago, mansr said:

How can I tell if they were nasty or just normal 240V shocks?

 

If you didn't get thrown across the room it was just a normal 240V shock.....

[sandyk]

12 minutes ago, mansr said:

How can I tell if they were nasty or just normal 240V shocks?

 

 It depends on how well grounded you are ?

Somebody of your experience shouldn't need to ask a question like this.

Try making contact with 240VAC , first when wearing rubber boots, then with bare feet and report back to the forum if you are still able to !

P.S.

 I have also had mild 240VAC shocks due to moisture ingress into a bathroom light switch.

Taking appropriate precautions, although not being qualified as an electrician, I replaced the switch and  put some sleeving over the wires to it for the protection of other family members. 

[mansr]

1 minute ago, Speed Racer said:

If you didn't get thrown across the room it was just a normal 240V shock.....

Then I've only experienced normal ones. I once touched a capacitor bank charged to 300V or so (thankfully not the full 1kV). That was a rather different experience from an AC mains shock.

[mansr]

4 minutes ago, sandyk said:

Try making contact with 240VAC , first when wearing rubber boots, then with bare feet

I assumed you'd be touching both the live and neutral (or safety ground) wires.

[sandyk]

10 minutes ago, Cornan said:

A simple 2-pole RCD/GFCI at the output will do to protect them for possible dangers.

 

Even they need to be periodically tested. Have you tested all yours recently, or just assumed that they are working correctly ?

Statistics show that in 230VAC (nominal)  countries, that qualified electricians who have training in this area, are quite often electrocuted, possibly due to complacency ?

[Cornan]

14 minutes ago, sandyk said:

 

 It depends on how well grounded you are ?

Somebody of your experience shouldn't need to ask a question like this.

Try making contact with 240VAC , first when wearing rubber boots, then with bare feet and report back to the forum if you are still able to !

 

Well, I have been in contact with 240v and it is not a nice experience I can tell you. My point is to educate instead of putting up causion signs. I know you mean well and care about people's safety. I admire that! However, at a certain point people become adults and need to care about their own safety. At that point it is crucial to educate the safety. Not only the safety of yourself, but the safety of your intire family. That's worth more than SQ for sure!

[One and a half]

1 hour 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.

 

Great post!

 

These findings tell me the amount of leakage is dependant on the frequency of the leakage. It's not DC, so anything other than DC, OK.

 

Cabled shields attenuate higher frequencies. The solid wire between equipment is to lower the potential differences between the source and the receiver, so the (higher frequency) leakage current sees the solid cable as opposition. This makes sense to me, since it's industrial practice and the systems seem to work OK.

 

So earthing the 0V line drops the common mode node reference, so any leakage current hasn't a chance to return?  

[One and a half]

Ahem. Earthing 0V supplies on systems that are designed for 5V, has nothing to do with 230V systems. 

 

Now I need to make up bonding wires.

[Cornan]

30 minutes ago, sandyk said:

 

Even they need to be periodically tested. Have you tested all yours recently, or just assumed that they are working correctly ?

Statistics show that in 230VAC (nominal)  countries, that qualified electricians who have training in this area, are quite often electrocuted, possibly due to complacency ?

 

Yes, I rest my RCD/GFCIs periodically. Approx. ones a moth. I do not trust them since I'm using portable devices.I also have a central RCD/GFCi in my appartment. That one I test ones a year.

[sandyk]

17 minutes ago, One and a half said:

Ahem. Earthing 0V supplies on systems that are designed for 5V, has nothing to do with 230V systems. 

 

 What  if we have a breakdown between Primary and Secondary sides of a 5V SMPS supply ?

Are they completely immune to such things due to their design ?

Just asking.