SMPS and grounding

[Ralf11]

How about... "Very system topology dependent" ??

 

BTW, Sandy just noted on another thread that the house gnd needs to be good - an issue for older dwellings.

[asdf1000]

14 minutes ago, Ralf11 said:

How about... "Very system topology dependent" ??

 

Ya, John already said that and I repeated it. A good message to hammer home again.

[Ekstatikon]

Dear users,

first of all, sorry for my bad english.

 

I need help to diagnose a problem, please.

 

The outlets in my apartment have no grounding. I hired an electrician to build one fully dedicated grounded outlet to power my system while all other outlets remained as they were. I connect the grounded socket to a double-conversion sinusoidal Nobreak online and I connect it to a power amplifier and an SMPS Meanwell, which powers an Uptone LPS-1, which feeds a Singxer SU-1 interface. All other elements (DAC, Macbook) are battery powered. Everything is OK.

Last night, I decided to do an experiment. I left only the power amplifier connected to the sinusoidal nobreak and transferred the Meanwell / Uptone LPS1 to the socket next door, to the phase shared with other apartment outlets without grounding, and ...

 

Bummmmm!

 

It burned a fuse of the amplifier. There was no major damage, I replaced the fuse and returned to the previous configuration.

What happened here?

Thank you.

[Ricardo007]

On 9/26/2017 at 2:20 AM, JohnSwenson said:

Hi tims,

I've covered this in many of my other posts, I'll try and distill it down.

 

Leakage currents are caused by some of the voltage from the AC line "leaking" into the DC output of a power supply. In the good old days this was caused by capacitance in the transformer in the PS, thus it was power line related, 60Hz - 120Hz -180Hz, etc. With the advent of SMPS supplies it has gotten WAY more complicated. In addition to the traditional line related frequencies there is a LOT of other frequencies related to the switching of the supply. These cover a broad range of frequencies and can go up into the MHz range.

 

The traditional leakage current (what you will find talked about if you search the web) is from the DC output of the supply to earth ground (the third pin on the power plug, "safety ground"). Since a lot of equipment today does not have a safety ground pin, you would think leakage current is not a problem anymore, but it turns out there is another path for leakage current: from the output of one power supply, through interconnects between boxes and through the other boxes power supply and back through the AC line, forming a loop. I call these "leakage loops".

 

Now leakage is kind of difficult to understand. We are used to thinking of "power supply noise" as being between the negative and positive wires of the supply. BUT leakage affects both - and + exactly the SAME thus there is no differential noise between - and +. Both - and + move up and down together , this is called "common mode" noise. Noise filters, regulators etc are ALL designed to work on the differential noise between - and + they don't touch the common mode leakage.

 

So what does leakage current DO? It travels from one box to another through the cables connecting them. This current primarily flows through the "shield" of the cable and induces a small voltage across the shield, this gets seen by the subsequent devices and winds up on the output going to the speakers. We have ALWAYS had leakage currents in any system that is AC powered, but recently these effects have been much larger than in years gone by.

 

In digital audio systems the fact that computers are almost always powered by SMPS has been a major change. Since the SMPS almost always have much more leakage than linear supplies we now have MUCH more leakage current going into the rest of our systems.

 

In addition there also seems to be a different kind of interaction going on with digital systems. For preamps, power amps etc the leakage just winds up as very low level, mostly low frequency noise on the output. BUT when this leakage current goes through a DAC it can modulate the clock in the DAC constantly slightly changing its frequency, this causes increased jitter on the clock, which causes distortion of the output waveform, which is very different from just adding low level noise.

 

In any given system there can be multiple sources of leakage current different places where it goes. Every system is going to be different in this regard, making it impossible to say "do this and you will have zero leakage".

 

I hope this helps.

 

John S.

Hi John, Hi All

 

Thanks for this very clear explanations.

 

I see another concept is "DC OFFSET" and some products adress this like:

http://www.kempelektroniks.nl/en/231/kemp-elektroniks/products/line-conditioners/power-dc-x-terminator

or

http://www.kempelektroniks.nl/en/231/kemp-elektroniks/products/line-conditioners/power-dc-x-terminator

How does this relate to what you are explaining?

How to the traditionnal approach of the ISOLATION TRANSFORMER

 

Are these 3 things remedies to the same problem OR complementary remedies???

 

Lastly:

Can John recipe be twisted and instead of linking the ground wire to the AC safety ground you connect to a GROUNDING BOX like ENTREQ? Has somebody experimented this?

 

Richard

[dongi]

Would this tweak do any good to linear PSU or only SMPS can benefit from it?

[JohnSwenson]

7 hours ago, dongi said:

Would this tweak do any good to linear PSU or only SMPS can benefit from it?

This is just for the high impedance leakage generated by SMPS. Linear supplies still have leakage but it behaves very differently. Some LPS can have significant amount of leakage others extremely small amounts.

 

BTW SMPS have both types, the same as LPS AND the high impedance type which is just SMPS produce.

 

John S.

[Cornan]

On 3/12/2019 at 3:01 PM, Ricardo007 said:

Can John recipe be twisted and instead of linking the ground wire to the AC safety ground you connect to a GROUNDING BOX like ENTREQ? Has somebody experimented this?

 

I use Entreq Minimus in this way. IME and in my perticular setup it sounds better than connecting it to the safety ground pin. The Minimus is also connected to the switch GND on my Aqvox network switch.

[Ricardo007]

I see another concept is "DC OFFSET"

a) How does this relate to what you are explaining?

b) How to the traditionnal approach of the ISOLATION TRANSFORMER

 

Are these 3 things remedies to the same problem OR complementary remedies???

[Ricardo007]

@John swenson

[Puma Cat]

On 10/28/2017 at 9:40 PM, Superdad said:

 

Yes, you got it perfectly!  And your clear summary stands well and very helpful alongside what John and I wrote.  This sort of stuff should be preserved somewhere to be useful to others.

 

 

 

All GREAT questions and ideas Greg!  

It's been a long day so answers and I-don't-knows will have to wait a day or so.  

As usual, you are on the right track.  And we are waiting on photos of your wild web of PS wizardry! 

Happy Sunday my friend,

--AJC

Absolutely OUTSTANDING set of articles.

 

This makes me want to think how one (we?) could do a DOE (Design of Experiments) to characterize all this, and understand which "control factors" interact and the impact they may have on the functional response, in this case, low- and high-impedance leakage currents. 

[Puma Cat]

Hi Gang,

I made up my own version of @JohnSwenson's high-impedance ground strap fix. I used the same terminal style male & female DC barrel/terminal plugs. Put two bare copper wires in each as John had orignally shown, attached 18 AWG stranded green silicone insulated wire, then I put a piece of heat-shrink tubing over the plugs/ground strap to give the assembly a little bit of mechanical stiffness. I also used these gray plugs that open from the top to attach the ground strap. These plugs are bit less bulky than the larger yellow ones. 

 

 

 

[Puma Cat]

The latest  in my high-impedance leakage current-defeating ground straps: Same DC barrel plug adapters with screw terminals and covered in heat-shrinkable tubing as above. This time, however, I used a Desco Ground Adapter that accepts a banana plug. Soldered on the banana plug, and put on a heat-shrink strain relief. This one will go on my LPS-1 power supply. 

[Steffenegede]

Hi, maybe I haven't been paying attention, but is it ok to connect multiple grounding cables to the same plug? The items are plugged in the same grounded power strip but I'm running out of outlets 😉

[JanRSmit]

I freed up an Netgear GS108E from my business network, and decided to measure the effect of grounding as described in this topic.

As you can see, the SMPS is connected to the electronics ground plane (EGP) and the EGP via small cap's connected to the chassis, via each of the four mounting screws.

I measure with my Fluke 8010 multimeter, the first generation FLUKE that measures flat in the audio band of 20Hz - 20KHz.

When i mention V-ac it is therefore the ac voltage measured over the entire frequency band the Fluke covers.

 

For grounding i use a cord of 1m connected at the safety earth of the AC-outlet where the SMPS is connected to only the N and L (the normal 2-pin connector).

The other end is used to connect to the chassis, the EGP or both. When this grounding is used, the  minus of the multimeter is also connected to this end of the grounding cable.

 

The SMPS when connected measures 12V DC and 0.2MV (AC)

 

I measured at 4 points:

p1: Chassis,

p2: EGP,

p3: Shield of connected SFTP patch cable, not connected on the other end.

p4: any of the 8 connections in the RS45 plug of the SFTPpatch cable (1m) on the open end.

 

Case 1: SMPS connected , no grounding whatsoever: p1: 87.5 V-ac ; p2: 89.1 V-ac ; p3: 86.7V-ac; p4: 78.9V-ac

Conclusion: a significant potential above 0 on each of the measured points. Cannot be  good 😉

 

Case 2: Chassis grounded: p1: 0.2mV ; p2: 26.0V ; p3: 0.2mV ; p4: 4.3-4.4V

Conclusion, better than Case 1, but still serious potentials in the electronics.

 

Case 3: The minus pole of the DC plug grounded (thus also the EGP): p1: 0.2mV ; p2: 0.1mV ; p3: 0.2mV ; p4: 0.2mV

Conclusion: a lot better. 😉 Note that to get to a stable low   low voltage of 0.1-0.2 mV took a few seconds, which can be the multimeter.

 

Case 4: As Case 3 plus chassis grounded as well: p1: 0.1mV; p2: 0.1mV ; p3:0.1mV ; p4: 0.1mV

Conclusion: measurement wise the best.

 

Wish i had a oscilloscope with spectrum analyzer, i then could have examined the frequnecy spectrum.

 

But overall conlusion: grounding , like described , and on this switch,  does matter. 

Next step: factor this switch into my IP chain connecting my NUC as one-node ROON server/endpoint.  And find out the audibility of these cases.

 

Note: in current IP chain, the root-switch (Ubiquity) has its chassis grounded, and that made a huge difference already. The SFTP cable from the root-switch to the IP45 outlet is of course earthed on the switch side, the patch cable connecting the NUC is an utp type, to prevent a ground loop.

 

 

 

 

 

 

[Superdad]

5 hours ago, Steffenegede said:

Hi, maybe I haven't been paying attention, but is it ok to connect multiple grounding cables to the same plug? The items are plugged in the same grounded power strip but I'm running out of outlets 😉

 

That should not be any problem at all. 

[Steffenegede]

54 minutes ago, Superdad said:

 

That should not be any problem at all. 

Great, thanks 😊👍

[charlesphoto]

7 hours ago, Steffenegede said:

Hi, maybe I haven't been paying attention, but is it ok to connect multiple grounding cables to the same plug? The items are plugged in the same grounded power strip but I'm running out of outlets 😉

 

I bought a short, four headed hydra pigtail extension cord from Amazon for mine. As long as you are on the same circuit, all is good. 

[jcn3]

8 hours ago, Steffenegede said:

Hi, maybe I haven't been paying attention, but is it ok to connect multiple grounding cables to the same plug? The items are plugged in the same grounded power strip but I'm running out of outlets 😉

 

i just bought a replacement plug and screwed several wires into the ground.

[Speedskater]

On 7/26/2019 at 3:27 AM, Steffenegede said:

Hi, maybe I haven't been paying attention, but is it ok to connect multiple grounding cables to the same plug? The items are plugged in the same grounded power strip but I'm running out of outlets 😉

Actually it can be a very good thing!

The basic definition for 'ground is:

"a common reference point"

So having all your Safety Grounds/Protective Earths connected to the same point is good. The less wire from one to another the better.

 

But having the DC supply common or audio circuit common connected to the AC outlet is bad. These grounds must be kept inside the chassis(s).

[Flyman]

Is there a reason that you are using male to female barrels adapter?!

 

as i see some companies are using spades that fits arround to the dc plug.

 

 

[HumanMedia]

On 7/31/2019 at 9:31 AM, Flyman said:

Is there a reason that you are using male to female barrels adapter?!

 

as i see some companies are using spades that fits arround to the dc plug.

 

 

 

I DIYed a version with a spade, and the connection isn’t the best and could easily disconnect. I can’t see a commercial version being much better unless it grips tightly around the barrel.

 

the plugs offer a much better connection. However if you find additional connectors affect the sound then the spade option could have less of an effect

[JohnSwenson]

The iFI groundhog does not use a common spade, it is very carefully designed so it is exactly the right size and has little "hooks" at the ends that go slightly more around the barrel than a common U spade. The result is that it "clicks" on and stays in place making a fairly decent connection.

 

John S.

[JanRSmit]

On 7/29/2019 at 11:22 PM, Speedskater said:

 

But having the DC supply common or audio circuit common connected to the AC outlet is bad. These grounds must be kept inside the chassis(s).

Hi Speed skater, can you elaborate on this? I am not sure i onderstand what you mean with "common"

[Speedskater]

12 hours ago, JanRSmit said:

Hi Speed skater, can you elaborate on this? I am not sure i onderstand what you mean with "common"

Because the word 'ground' has so many different meaning, circuit common is specific.

The DC supply 0V can be connected to the inside of the chassis. The chassis is probably connected to the Safety Ground. But you should not run an insulated wire from the DC 0V out to the Safety Ground.

Just because there is continuity from one Ground to another, does not make them the same Ground.

[JanRSmit]

14 hours ago, Speedskater said:

Because the word 'ground' has so many different meaning, circuit common is specific.

The DC supply 0V can be connected to the inside of the chassis. The chassis is probably connected to the Safety Ground. But you should not run an insulated wire from the DC 0V out to the Safety Ground.

Just because there is continuity from one Ground to another, does not make them the same Ground.

I understandy youruse of common.

Whether the chassis is connected to safety ground is a dangerous assumption.

With electronics with a 2-prong mains plug it is not.

Whether it is connected to the common as you defined it and if so how is another thing you should not assume.

 

Connecting the chassis (case) if it is metal to safety ground (the thirth prong on the mains plug) is a must. This also implies the requirement that the safety ground on the outlet is proper functioning.

In case of a Netgear switch i have it is not. (2 prong plug) Thus i need to create a connection to safety ground.

In other words you have to check.