SMPS and grounding

[agladstone]

7 minutes ago, ElviaCaprice said:

After further listening, plugging in the ground plug and unplugging, my observations are that on my system this DIY grounding has no noticeable effect.

I wonder if your results would be different if you had the ground leads from the plug going into the screw on DC plugs negative as John Swenson had detailed as opposed to using spade lugs? I’m assuming that you have these spade lugs going to a screw on the chassis? 

It’s possible that they’re not as effective or the same as going to the negative of a DC connector? I’ve tried to ground the RCA cable going from my Pre-Amp to my subwoofer in the past using Spade Lugs to metal chassis with no results and later concluded that since the metal chassis and screws were painted, that it’s very possible the paint was blocking the ground connection? 

[ElviaCaprice]

1 hour ago, agladstone said:

I wonder if your results would be different if you had the ground leads from the plug going into the screw on DC plugs negative as John Swenson had detailed as opposed to using spade lugs? I’m assuming that you have these spade lugs going to a screw on the chassis? 

It’s possible that they’re not as effective or the same as going to the negative of a DC connector? I’ve tried to ground the RCA cable going from my Pre-Amp to my subwoofer in the past using Spade Lugs to metal chassis with no results and later concluded that since the metal chassis and screws were painted, that it’s very possible the paint was blocking the ground connection? 

Could be?

But I always thought the outside barrel of the DC plug was the ground.  If the spade is making contact here it should be just as good as the first JS suggestion.  Also latter he suggests using the spade on the Ifi product.

[sandyk]

The outers of the sockets aren't necessarily connected to a metal chassis.

This means that you may be able to connect the earthing as John described, to say an RCA plug , plugged into a not in use RCA socket , without a connection to the inner of the plug.

 

If you have a DVM you can check whether or not the outers of the sockets are connected to the metalwork. You may also need to scrape away the anodising around a mounting screw to get a good contact.

You often need to do this with cases used for DIY projects in order to give decent screening, and continuity of the screening between front, back, top and bottom, and side panels.

[gstew]

3 hours ago, ElviaCaprice said:

After further listening, plugging in the ground plug and unplugging, my observations are that on my system this DIY grounding has no noticeable effect.

I may be missing something... if so, please forgive me.

 

I don't see in your post that you were grounding the negative side of SMPS outputs (like the Meanwell). As I understand it, the grounding trick is designed to sharply reduce the amount if 'high-impedance' noised transmitted from the SMPS into the powered unit. 

 

Is what I'm missing that you were using Meanwells to energize the LPS-1s? 

 

Or is something else?

 

Pictures maybe?

 

Greg in Mississippi

[ElviaCaprice]

8 minutes ago, gstew said:

I may be missing something... if so, please forgive me.

 

I don't see in your post that you were grounding the negative side of SMPS outputs (like the Meanwell). As I understand it, the grounding trick is designed to sharply reduce the amount if 'high-impedance' noised transmitted from the SMPS into the powered unit. 

 

Is what I'm missing that you were using Meanwells to energize the LPS-1s? 

 

Or is something else?

 

Pictures maybe?

 

Greg in Mississippi

Greg, that is exactly what I'm doing.  All my LPS-1's are powered by a meanwell.  So I stuck the spade of the grounding wire to the outside barrel of the lead running from the meanwell to the LPS-1 input.  At the input, the spade is attached to the outside of the barrel (is not the outside of the barrel the negative) and plugged in to the input of the LPS-1, trapping the spade onto the barrel. 

Is this not correct?

[gstew]

On 10/2/2017 at 2:19 PM, JohnSwenson said:

Any electrical signal (useful or noise) has a "source impedance". You can think of this as a resistor the signal has to go through before it gets to where you are looking at it. It is an impedance because it can vary with frequency.

 

As a concrete example, lets say your source has an impedance of 1k ohms, if you apply that to a 1k ohm resistor to ground, the signal level will be cut in half. That is actually how you usually measure output impedance, run the input through a known resistance to ground and measure the level across the resistor, the output impedance acts as a voltage divider with the known resistor, from the resulting voltage you can calculate the source impedance.

 

For any given "noise source" there is at least one mechanism generating that noise. The mechanism will have a particular impedance associated with it. In many cases more than one mechanism is involved with generating noise, each of these mechanisms may have a different output impedance. There may also be different frequency response issues with the different mechanisms.

 

This seems to be the case with SMPS, there seems to be at least two different mechanisms that cause the leakage and they seem to have very different impedances. I don't know what those mechanisms ARE, i have not spent time in figuring that out, I'm not really interested in building my SMPS so I don't really care what actually causes it, especially since it will take a LOT of work to find out and I would much rather spend my time working on other things.

 

Leakage current causes issues in audio systems when it flows through a conductor, creating a voltage across that conductor which causes something to not behave the way you would like it. In some cases this is just directly creating noise on the shield of an interconnect and the receiving circuit sees this as noise. In a DAC this can show up as noise developed on a ground plane that can modulate an oscillator causing increased jitter on the clock.

 

There are two ways you can attenuate the leakage noise, you can put a resistance in series with it, or you can shunt it. Lets cover both of the separately.

 

The series resistor form works like this: you have the source impedance and you stick a resistor in series. Lets look at some possible values and outcomes. Say 100 ohm output impedance and you put 1 mega ohm in series, that is going to attenuate the noise drastically. But what if the source is 100 mega ohms, then that 1 mega ohm resistor is not going to do very much (a VERY slight attenuation). So for high impedance series resistor works good for lower impedance source, but not well for high impedance source.

 

The shunt form works by shunting the source around your source around the "test point", frequently to ground. Say you have the 100 ohm source and you shunt with 1 mega ohm, nothing happens, but of the source is 100 mega ohms, that 100 mega ohm shunt will dramatically decrease the amplitude.

 

I know the output of the SMPS is a combination of impedances by running a bunch of these shunt and series tests with different values and seeing what I get. The only way to get the results I saw is if the source consists of both high impedance and low impedance components at the same time.

 

The upshot is that it takes BOTH methods to get rid of the noise, both a shunt and a series.

 

John S.

 

 

 

 

John,

 

Many thanks for the explanation. Once you brought in the term 'source impedance', it all started to make sense!

 

AND then you had to go and give more details! I now know a lot more about noise production mechanisms and how one goes about detecting them and eliminating them than I ever thought there was to know! VERY USEFUL!!!

 

DANG, you give great explanations!

 

Again, THANKS!

 

Greg in Mississippi

[gstew]

1 minute ago, ElviaCaprice said:

Greg, that is exactly what I'm doing.  All my LPS-1's are powered by a meanwell.  So I stuck the spade of the grounding wire to the outside barrel of the lead running from the meanwell to the LPS-1 input.  At the input barrel the spade is attached to the outside of the barrel and plugged in to the input of the LPS-1, trapping the spade onto the barrel. 

Is this not correct?

Thanks for the clarification.

 

Yup, what you did should ground out that darned old 'high-impedance' SMPS noise. 

 

Sounds like it is all working as it should to me.

 

While I now use only linear supplies to power my LPS-1s, I did get my 1st 2 with Meanwells. While I had some issues with buzzing in my setup (where the buzz was induced into a TVC in certain situations), I couldn't hear any difference in the performance of the gear I powered by those LPS-1s whether energized by the Meanwells or a couple of linear supplies. 

 

Greg in Mississippi

[mansr]

10 hours ago, ElviaCaprice said:

But I always thought the outside barrel of the DC plug was the ground.

Usually, but not always.

[JohnSwenson]

13 hours ago, sandyk said:

 

 

Comments Please ?

 

Alex

Highly unlikely.

 

Traditional "ground loop" which most articles on audio ground loop talk about is caused by induction of AC (hot/neutral) to safety ground. This only shows up if there is a long distance run of line wiring from one location to another. Such as you have 200 feet between your preamp and power amp. This CAN happen between components that are close together IF they are on different circuits and there is a long distance back to the panel.

 

In all the playing around with leakage testing I have been doing, including between circuits with a long path back to the panel, I have not once had a case of traditional ground loop, it has all been leakage.

 

So the probability of fixing leakage issues with ground is VASTLY higher than it will cause a traditional ground loop.

 

If someone is actually getting nasty buzzing when grounding chassis  there is probably something wrong with the wiring.

 

John S.

[sandyk]

2 hours ago, JohnSwenson said:

This CAN happen between components that are close together IF they are on different circuits and there is a long distance back to the panel.

 

Hi John

 In my case I have 2 different AC mains feeds along the wall behind my gear, which I need to use rather than a huge power board behind the gear.  I must admit though, that in my system I have no evidence of audible mains hum, but I have gone to a great deal of trouble to reduce the possibility of such problems.

BUT, mains hum is not the ONLY indicator of inadvertent ground loops is it ?

Correct earthing is of vital importance, especially with Computer Audio, and USB especially.

 

Kind Regards

Alex 

[John769]

FWIW, I've noticed more bass and darker background when the ground wire is attached directly to the negative banana plug (on the Gophert smps) compared to wrapping it around the screw terminal.  The wire goes to a ESD plug on my powerstrip.

 

 

[Cornan]

49 minutes ago, John769 said:

FWIW, I've noticed more bass and darker background when the ground wire is attached directly to the negative banana plug (on the Gophert smps) compared to wrapping it around the screw terminal.  The wire goes to a ESD plug on my powerstrip.

 

 

 

Interesting John769!

I have actually ordered these fork spades a while ago to try at the screw terminals of my Gopherts just to see if better contact at the banana plugs will translate to better SQ http://www.ebay.com/itm/Y-U-Type-Brass-Speaker-Plugs-Audio-Screw-Fork-Spade-Connector-Gold-Plated-Plug/142466085228?ssPageName=STRK%3AMEBIDX%3AIT&var=441464685440&_trksid=p2057872.m2749.l2649

 

Based on your impressions it looks like it could be a good move!

 

 

[mourip]

This is a great thread. It is definitely why I keep coming back to CA.

 

I have a question regarding the broad concepts discussed here but not specifically involving an Uptone product.

 

What about a device that has an internal SMPS that is fed via an external IEC socket and connected to a three plug AC cable. Is it most likely that given the fact that there is a ground pin being used that the SMPS has a ground connection to it or is it more likely that the ground pin is just a chassis safety ground?

 

I can probably answer my own question with "It depends on how it was designed" however is there any harm to making sure that the negative output of the SMPS is in fact tied to the IEC ground or would this be ill advised?

 

Regarding personal electrical safety I have done a lot of DIY and scratch building and am comfortable making that kind of a change.

 

Thanks!

[Cornan]

5 hours ago, mourip said:

This is a great thread. It is definitely why I keep coming back to CA.

 

I have a question regarding the broad concepts discussed here but not specifically involving an Uptone product.

 

What about a device that has an internal SMPS that is fed via an external IEC socket and connected to a three plug AC cable. Is it most likely that given the fact that there is a ground pin being used that the SMPS has a ground connection to it or is it more likely that the ground pin is just a chassis safety ground?

 

I can probably answer my own question with "It depends on how it was designed" however is there any harm to making sure that the negative output of the SMPS is in fact tied to the IEC ground or would this be ill advised?

 

Regarding personal electrical safety I have done a lot of DIY and scratch building and am comfortable making that kind of a change.

 

Thanks!

 

+1 I would be very interested to know this as well. My Brooklyn DAC have a SMPS connected to a grounded IEC. Just thinking out loud. If the IEC is connected to the chassi, would'nt a ground wire from chassi to safety ground (or grounding box) do pretty much the same thing as internally rewiring the IEC socket so it is connected to the safety ground?

 

Looking at a picture inside Brooklyn DAC it does look like the SMPS is actually connected to the IEC ground pin.

 

[Superdad]

6 hours ago, mourip said:

What about a device that has an internal SMPS that is fed via an external IEC socket and connected to a three plug AC cable. Is it most likely that given the fact that there is a ground pin being used that the SMPS has a ground connection to it or is it more likely that the ground pin is just a chassis safety ground?

 

I can probably answer my own question with "It depends on how it was designed" however is there any harm to making sure that the negative output of the SMPS is in fact tied to the IEC ground or would this be ill advised?

 

Hi Paul, really nice to see you here!

 

Indeed the answer is "depends on how it was designed."

While we (UpTone, myself, John S.) are NOT advising anyone to open up their AC powered devices or to stick fingers inside (while standing in a puddle of water in a rainstorm ), it should be rather easy to check.

 

We are talking about determining if the DC output ground of the SMPS is common to the AC mains safety ground.   So all you need do--with POWER OFF please--is put one probe of a continuity checker (the beeping setting of your multimeter) on whichever terminal of the internal SMPS is not the +DC (avoiding calling it "ground" on purpose), and the other probe on the ground pin of the IEC inlet.

 

If you get a beep then the output of the device's SMPS is already grounded.  If not, well then it is up to you as to if you wish to ground it (may void warranty, don't blame us for damage, etc.).

 

Cheers,

 

--Alex C.

[Superdad]

44 minutes ago, Cornan said:

 

+1 I would be very interested to know this as well. My Brooklyn DAC have a SMPS connected to a grounded IEC. Just thinking out loud. If the IEC is connected to the chassi, would'nt a ground wire from chassi to safety ground (or grounding box) do pretty much the same thing as internally rewiring the IEC socket so it is connected to the safety ground?

 

Not entirely following you.  We are talking about grounding the (non-positive) OUTPUT of the SMPS.  So it really depends upon if the ground-plane of the circuit board is common with the chassis (which IS most likely common to AC mains ground).  There is a chance that only the SMPS INPUT is grounded to the chassis/inlet.  You would need to use a meter to check.

 

44 minutes ago, Cornan said:

 

Looking at a picture inside Brooklyn DAC it does look like the SMPS is actually connected to the IEC ground pin.

 

Well again, the SMPS input is most assuredly connected to the IEC ground pin.  But the photo does not give enough detail to tell if the OUTPUT of the supply is.  I see just the two black wires going to the PCB.

[Cornan]

28 minutes ago, Superdad said:

 

Not entirely following you.  We are talking about grounding the (non-positive) OUTPUT of the SMPS.  So it really depends upon if the ground-plane of the circuit board is common with the chassis (which IS most likely common to AC mains ground).  There is a chance that only the SMPS INPUT is grounded to the chassis/inlet.  You would need to use a meter to check.

 

 

Well again, the SMPS input is most assuredly connected to the IEC ground pin.  But the photo does not give enough detail to tell if the OUTPUT of the supply is.  I see just the two black wires going to the PCB.

 

Thanks Alex! ?

 

I was thinking that the output of the SMPS was connected to the chassi, but on the other hand if the IEC output is connected to the chassi the SMPS would actually be common with AC ground. Sorry, I wrote before I thought things through completely! ?

 

Looks like it is time to ask Mytek support about it and if they do not answer I'll dig out my multimeter from the drawer and measure DC - OUTPUT to safety ground pin continuity or simply add a external floating SMPS with DC- grounding to the Brooklyn DAC. ?

[d_elm]

Received today an order of DC connector pairs and installed them on the Meanwell SMPSs for the microRendu and the downstream FMC, both powered by LPS-1.  I cannot stop listening, fantastic.  Next step is to compare fibre to a Netgear FS105 v3 with the switch's SMPS having an adapter.  Thank you John !

[mourip]

6 hours ago, Superdad said:

 

Hi Paul, really nice to see you here!

 

Indeed the answer is "depends on how it was designed."

While we (UpTone, myself, John S.) are NOT advising anyone to open up their AC powered devices or to stick fingers inside (while standing in a puddle of water in a rainstorm ), it should be rather easy to check.

 

We are talking about determining if the DC output ground of the SMPS is common to the AC mains safety ground.   So all you need do--with POWER OFF please--is put one probe of a continuity checker (the beeping setting of your multimeter) on whichever terminal of the internal SMPS is not the +DC (avoiding calling it "ground" on purpose), and the other probe on the ground pin of the IEC inlet.

 

If you get a beep then the output of the device's SMPS is already grounded.  If not, well then it is up to you as to if you wish to ground it (may void warranty, don't blame us for damage, etc.).

 

Cheers,

 

--Alex C.

 

Thanks for the input and the warnings. Always good practices to remember.

 

I earned a pacemaker at a somewhat early age and so now tend to avoid electrocution. Plus my wife said she would kill me if I died.

 

No sense stressing her  :-)

 

[mozes]

1 hour ago, d_elm said:

Received today an order of DC connector pairs and installed them on the Meanwell SMPSs for the microRendu and the downstream FMC, both powered by LPS-1.  I cannot stop listening, fantastic.  Next step is to compare fibre to a Netgear FS105 v3 with the switch's SMPS having an adapter.  Thank you John !

I am late to the SMPS grounding party, do you mean that you grounded the negative output of the Meanwell SMPSs that energize the LPS-1s and heard a boost in SQ?

 

[d_elm]

2 minutes ago, mozes said:

I am late to the SMPS grounding party, do you mean that you grounded the negative output of the Meanwell SMPSs that energize the LPS-1s and heard a boost in SQ?

 

Immediate and all music.  Amazing what lower noise will do.

[mozes]

Just now, d_elm said:

Immediate and all music.  Amazing what lower noise will do.

Thank you, I will try it!

[ElviaCaprice]

Mozes, I grounded out my 4 active LPS-1s and two DC outputs from my HDPlex.  I found no difference in SQ.  It's easy to do, so worth a try.

[asdf1000]

I've found grounding the 2 x SMPS's right before my  Hugo2 headphone setup has improved things. Grounding the router and powered USB hub and other things further upstream of the DAC have made less difference in my system.

 

The Hugo2 is powered by an iFi 5V at 2.5A (the Hugo2 needs >2.1A so I can't use an LPS-1 unfortunately, otherwise I would) with the iPower's DC plug now grounded with John's method. Except during really critical listening sessions I unplug the power supply completely. But 90% of the time, I prefer to keep the Hugo2 powered by the 5V iPower anyway. So a combination of the ~1uV 5V iPower and now lower leakage current makes for a better low cost PSU. 

 

The Hugo2's USB audio input is fed by an Iso Regen + LPS-1, with the latter's Mean Well's DC plug also now grounded with John's method.

 

So those 2 changes right before the Hugo2 DAC have really improved things more than grounding further upstream. More bass, more detail, less listening fatigue. Not earth shattering but noticeable improvements (for cheap too).

 

But I can tell John is so passionate about doing these the right way, so even if the further upstream grounding doesn't have as much as an audible improvement in my system (it MAY in others systems of course) I kind of want to do it right also, so I'll keep whatever I can grounded.

 

It's not that expensive to do. Thanks @JohnSwenson !

 

PS: can you share what this grounding method does with the iFi iPower's leakage current, which you said previously measured the worst of your tested SMPS's? And can you share if the number drops to the levels of typical linear PSU's?

 

Cheers

[sandyk]

I don't particularly like the idea of grounding the case/ 0 volts rail of SMPS gear that wasn't designed to be earthed.

I am more concerned about retaining the existing safety factor when using 230VAC.

 

 When I get the chance, and obtain a 3 pin mains plug, I will try what Silicon Chip magazine did, which was to connect a 100 ohm .25W resistor to earth, which reduced the leakage voltage to a much lower level for measurement purposes, then try connecting a 22nF capacitor across the 100 ohms to mop up HF rubbish like they did .

100 ohms will not be low enough to cause any earth loop problems, although in the majority of cases a direct connection to mains earth won't either, as John has already said.

 I also checked my Oppo 103 which is SMPS powered, but it uses a 3 pin mains plug, and has no measurable AC  voltage to mains earth from it's chassis..

The STB that I will be trying this on, is powered from a separate mains feed to my main gear, so the chance of a minor mains loop is a little higher than normal..

Alex