SMPS and grounding

[octaviars]

9 minutes ago, Cornan said:

The green/yellow cable is a ground wire ofcourse. It would be really dangerous without the IEC inlet grounded.

 

Yes but what is the ground used for on the PCB? If the chassi is isolated why would it be dangerous if there was no earth? 

 

I just want to know what they use the earth for if it is not connected to the chassi for safety reasons and if the chassi is not grounded it must be double isolated. I suppose the connect the filter capacitors to ground.

[Cornan]

12 minutes ago, octaviars said:

 

Yes but what is the ground used for on the PCB? If the chassi is isolated why would it be dangerous if there was no earth? 

 

I just want to know what they use the earth for if it is not connected to the chassi for safety reasons and if the chassi is not grounded it must be double isolated. I suppose the connect the filter capacitors to ground.

 

If you want to know more in details I suggest you ask the supplier for answers. They are usually quite quick to reply on Banggood.com.

The safety ground connection should be there for personal safety if something goes wrong.

[octaviars]

45 minutes ago, Cornan said:

The safety ground connection should be there for personal safety if something goes wrong.

 

Yes that is of course the main purpose but if the chassi is not connected to safety ground how will it protect anyone if something goes wrong inside. If the unit was double isolated it would not have any ground connection.

 

This got really of topic so I will leave it for now and check when my own Ghopert arrives. 

[sandyk]

Hi John

 The safety, and potential damage aspect of inexperienced members doing what you are suggesting worries me a little. (and may also contravene FCC requirements ?)

 Perhaps a compromise of something like a series 10 ohm .25W resistor at the equipment end of the added earth wire may be a good compromise ,and still be quite effective ? The series resistor could be inside a small length of heat shrink.

 

 Regards

Alex

[tims]

Appreciate it someone could explain what the effects these leakage currents have on different components and how they affect SQ. There's been a lot written about them recently but I'm still unclear about what they are and why we should minimiize them.

A link to another post explaining more would be fine.

 

Thanks.

[sandyk]

Please check your PMs

 

Alex

[mike eastman]

John,  can you connect more than one of the adaptors to the same plug ? Any reason you couldn't eliminate the plug and connect the wire direct to ground wire in receptacle box?

[JohnSwenson]

3 hours ago, mike eastman said:

John,  can you connect more than one of the adaptors to the same plug ? Any reason you couldn't eliminate the plug and connect the wire direct to ground wire in receptacle box?

Yes you could ground more than one SMPS from the same wire, just remember that the ground needs to come from the same circuit, preferably the same power strip/outlet box as the SMPS. So say you have two SMPS plugged into the same strip, then yes grounding them from the same wire is fine.

 

You COULD ground an SMPS from a wire connected to ta metal box IF that box is known to be grounded. I'm not going to be responsible for people taking outlet boxes apart to get to a ground wire.

 

John S.

[asdf1000]

On 20/09/2017 at 12:27 PM, JohnSwenson said:

You may ask "how effective IS this?"

 

Here are some graphs, the first is the leakage current of an SMPS, the second is with this adapter plugged in:

 

Hi John, do these leakage current levels with this adapter method, come down to linear PSU leakage current levels?

 

Just speaking in terms of leakage current levels, not DC voltage noise/ripple of course.

 

 

[JohnSwenson]

Remember the leakage from an SMPS contains both high impedance and low impedance components, the ground shunt gets rid of the high impedance components. The low impedance components are still left. These components are usually still greater in amplitude than many linears, but some linears might be a bit more.

 

BUT since what is left is the low impedance components, they CAN easily be blocked.

 

You can do the same thing with linears, which gets rid of THEIR high impedance components, just leaving the low impedance components, which are REALLY low.

 

I'm putting together another post in the next few days that shows how this works with network systems (I'll post that in the thread on the Sonore forum).

 

John S.

[JohnSwenson]

There are some ways to make this grounding easier to do for different size connectors, I will be making a post on this probably tomorrow night, stay tuned!

 

John S.

[asdf1000]

10 minutes ago, JohnSwenson said:

stay tuned!

Cheers John!

[JohnSwenson]

I've been experimenting with some ways to make the SMPS a little easier or applicable to a broader range of equipment. First off is a way to use it with equipment that does not have a 5.5x2.1 barrel jack.

 

I found another I had on hand, in this case the 7.5V Mean Well, this was exactly the voltage my switch took, IT plugs into the adapter, then a 5.5x2.1 to something else is used to plug into the device. In this case it was one of the adapters that came with the iPower. This works great. Using this technique I was able to ground the power to a bunch of different devices that had different plug sizes.

 

Both Amazon and Ebay have kits of these adapters available which include many different plug types.

 

Next up is an interesting kit from iFi called the Groundhog. It has a gounding system and several adapters to ground equipment in various ways. The one most appropriate is this:

 

This kit is unusual, it contains an IEC SOCKET, not a plug, you plug in a standard IEC power cord for your country. Most of you will already have several of these in your cable drawer. It doesn't matter what the country is, the IEC end is the same so they will plug right into the Groundhog. They call the adapter I show plugged in the "DC Spade", it is actually a little clip designed to clip onto the barrel of a 5.5 plug, thus grounding it. Clip it onto the barrel, then just plug it in.

 

This replaces the adapter shown in the first post with an off the shelf system you can buy, you don't have to build anything yourself. It is not dirt cheap, ($49), but for those that don't want to deal with building the adapter it is a nice alternative. It does exactly the same thing - it grounds the negative DC output of a power supply.

 

I hope this makes it a bit easier for people to try this approach.

 

John S.

[JohnSwenson]

On 9/23/2017 at 10:45 PM, tims said:

Appreciate it someone could explain what the effects these leakage currents have on different components and how they affect SQ. There's been a lot written about them recently but I'm still unclear about what they are and why we should minimiize them.

A link to another post explaining more would be fine.

 

Thanks.

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.

[austinpop]

6 hours ago, JohnSwenson said:

I've been experimenting with some ways to make the SMPS a little easier or applicable to a broader range of equipment. First off is a way to use it with equipment that does not have a 5.5x2.1 barrel jack.

 

I found another I had on hand, in this case the 7.5V Mean Well, this was exactly the voltage my switch took, IT plugs into the adapter, then a 5.5x2.1 to something else is used to plug into the device. In this case it was one of the adapters that came with the iPower. This works great. Using this technique I was able to ground the power to a bunch of different devices that had different plug sizes.

 

Both Amazon and Ebay have kits of these adapters available which include many different plug types.

 

Next up is an interesting kit from iFi called the Groundhog. It has a gounding system and several adapters to ground equipment in various ways. The one most appropriate is this:

 

This kit is unusual, it contains an IEC SOCKET, not a plug, you plug in a standard IEC power cord for your country. Most of you will already have several of these in your cable drawer. It doesn't matter what the country is, the IEC end is the same so they will plug right into the Groundhog. They call the adapter I show plugged in the "DC Spade", it is actually a little clip designed to clip onto the barrel of a 5.5 plug, thus grounding it. Clip it onto the barrel, then just plug it in.

 

This replaces the adapter shown in the first post with an off the shelf system you can buy, you don't have to build anything yourself. It is not dirt cheap, ($49), but for those that don't want to deal with building the adapter it is a nice alternative. It does exactly the same thing - it grounds the negative DC output of a power supply.

 

I hope this makes it a bit easier for people to try this approach.

 

John S.

 

Hi John,

 

Many thanks for for this simple DIY solution.

 

Would you consider this necessary with non-floating LPSUs like the HDPlex? I am powering my upstream switch, router, and modem with one of these, and wonder if I should be using these techniques to ground?

 

Also, would you get similar benefits by using a little IT like the B&K 1604A? Obviously this isn't the ultra low capacitance Topaz, but just wondering what your measurements show?

 

[Ryelands]

8 hours ago, rickca said:

Does grounding the SMPS mean using an LPS is no longer as compelling an idea?

 

As what follows is a bit off-topic wrt Sonore thread, I'm chipping in here. I hope that's OK but move/delete as appropriate.

 

I've been powering the downstream end of a music-system-only LAN with an LPS-1 for several months now. I have neither the wit nor the kit to replicate John's fascinating measurements but I'd be surprised if an SMPS, however well configured, were to better the LPS-1. As I experimented over months to get where I am now, I'll describe my setup. It might be of wider interest.

 

A TP-Link FMC feeds music data from a remote server (OK, an old XP box in the back room) and passes it through an EMO EN-70 LAN isolator to a Zytec ES105A switch. That switch connects to a second switch which connects to a third which connects via another EN-70 to the elderly Fit-PC2 I now proudly call my Network Audio Adapter.

 

The LAN devices connect to the LPS-1 via home-made, 24awg quad-core cables. The Fit-PC2 has its own LPS-1 and connects to an Intona USB isolator also powered by its own LPS-1. I think I can honestly describe my digital "front end" as off-grid.

 

The LAN cables are made from decent (Excel) CAT5 stock and Telegartner connectors. The system runs at 10MB/sec, allowing cable pairs 3 & 4 to be omitted. That tweak definitely matters. The cables are screened using self-adhesive Cu sheet, each with a JSSG-style drain wire. (My wife says that all that shiny copper makes the rack look like a tart's dressing table. I can't say.)

 

The lesson for me was that if I change ANY part of the above almost absurdly elaborate chain I lose sound quality (SQ). If I swap in even a decent LAN cable, remove one of the isolators, by-pass even one of the Zyxel switches, I lose SQ. The Meanwell SMPSs that run the LPS-1s are powered via an isolating transformer. If remove the transformers, SQ falls. If I leave all four pairs in the LAN cables, SQ falls. If I run the LAN at 100MB/sec, SQ falls sharply.

 

Worse, though I already knew that Zyxel switches typically sounded better than other makes and that all the 10/100 switches I tried sounded better than a Netgear Gigabit switch, when by chance I swapped one of the Zyxel v3 switches for a Zyxel v1, SQ improved sharply. (Different controller chips.) It also improved when I made the cases "sort-of Faraday shields" by filing away paint so the metal base made proper contact with the lid.

 

I could have tried one of those "audio grade" switches but it seems they all use Gigabit-speed devices and are not cheap.

 

All that said, SQ has very much improved. I'm not talking "more inner micro-detail in the singer's mid-range" or the like: what I got was a Wham-Bam in your face improvement. The system came alive even though in essence all I'd changed was the network cable between a server and a NAA. It suggests to me that the signal quality is markedly better than what I've been used to for several years now or, put a different way, LAN links are almost as pollutant as KVMs.

 

BTW, when I replaced the decent linear PS that drove the server end of the link (3 more Zyxel v1 switches and FMC but no isolators) with a USB charger thingie, SQ again improved. I plan to try an LPS-1 there when funds permit.

 

I'm not suggesting the chain could not be simplified, only that I don't at present know where to begin despite John saying "you will have to use something like the LPS-1 which will get rid of it all". The LPS-1 is superb at powering LAN devices but IME it's only a start.

 

[Theobetley]

Its amazing what a clever audiophile can do with no measuring equipment, no latest and greatest operating system...just his ears and a healthy curiosity to experiment. I don't think anyone else has come up with eliminating wires within an ethernet cable and running 10/100 in the ethernet driver. Well done Dave.

[Ryelands]

15 minutes ago, Theobetley said:

I don't think anyone else has come up with eliminating wires within an ethernet cable and running 10/100 in the ethernet driver.

 

The 10/100 thing came from a passing remark in a post by John S a while back about Gigabit drivers being much more complex and busy, which makes sense. I did think up the wire-snipping bit all by myself but have since been told (rather snootily) that it's been done before.

 

BTW, I found a big difference between running at 10 and 100 MB/sec. Easy enough to try in many systems.

[mansr]

21 minutes ago, Ryelands said:

The 10/100 thing came from a passing remark in a post by John S a while back about Gigabit drivers being much more complex and busy, which makes sense.

The Ethernet drivers I've written or otherwise looked at work exactly the same regardless of the actual link speed. If you want to ensure the driver code is as simple as possible, you need to choose hardware accordingly. High-end server NICs (Intel, Broadcom) are the most complex, embedded controllers in SoCs the simplest. For use in a PC, I'd suggest finding an old PCI card such as a 3com 3c900 series. Those are simple and reliable. I think I still have a few in a box somewhere.

 

Of course, I don't believe any of this actually matters. I'm merely pointing out that forcing a lower link speed isn't going to do much at the software level, so if you think this is important, you're going about it the wrong way.

[rickca]

14 hours ago, JohnSwenson said:

it grounds the negative DC output of a power supply

OK here's a really stupid question.  Why don't they make SMPS with negative DC output grounded in the first place?

[Ryelands]

1 hour ago, mansr said:

Of course, I don't believe any of this actually matters. I'm merely pointing out that forcing a lower link speed isn't going to do much at the software level, so if you think this is important, you're going about it the wrong way.

I don't have the advantage of belief but I have experimented at length with LAN-related variables in an audio context. My only regret is that I didn't do it years ago.

 

I didn't advance an hypothesis as to why link speed might affect SQ nor am I clear what "the software level" is.

 

In light of John's passing remark, I did a five-minute trial, heard a worthwhile improvement and so continued to experiment at length. Mostly successfully.

 

I've repeated the trials on different systems with all the usual precautions. Others kind enough to repeat them on their systems generally confirmed what I reported.

 

I accept what you say about older NICs. Both systems I use as described link to the audio adapter via 10/100 PCI Realtek NICs at least 10 years old, probably more.

[Superdad]

39 minutes ago, rickca said:

OK here's a really stupid question.  Why don't they make SMPS with negative DC output grounded in the first place?

 

Yeah, I've been wondering that for weeks now since John starting playing with this during measurement sessions.  Probably has something to do with regulatory requirements.  A lot of the European regs are very strict with regards to what goes back into the mains--caring less about what comes out of the DC end.

I sent John a low-leakage "medical" Mean Well for testing a while ago.  It would be funny if the difference with that one was its grounding.  I'll ask him to check it.

 

Speaking of grounding--but not to be confused with this grounding of the output topic--I recently discovered (upon opening one) that although the Mean Well we offer for REGENs and LPS-1s has a 3-pin, IEC320-C14 socket, that ground pin is not connected to ANYTHING inside the SMPS!

(I still prefer to provide that style of unit--versus wall-wart or figure-8 C7 inlet--so that we don't have to stock and keep track of wall plugs/cables for all countries.  Everyone gets a 50cm USA cord that fits in the package and they can toss it or cut the end and put on a local plug--or whatever.)

[mansr]

19 minutes ago, Ryelands said:

I don't have the advantage of belief but I have experimented at length with LAN-related variables in an audio context. My only regret is that I didn't do it years ago.

 

I didn't advance an hypothesis as to why link speed might affect SQ nor am I clear what "the software level" is.

 

In light of John's passing remark, I did a five-minute trial, heard a worthwhile improvement and so continued to experiment at length. Mostly successfully.

A gigabit phy may well be less electrically noisy when operating at 100 Mbps. It is, after all, a much simpler system. By "software level" I meant OS drivers and other related software. I was under the impression you had hoped that the driver would put less load on the CPU and thus cause less noise if the link speed was reduced. Sorry if I misunderstood you.

[rickca]

44 minutes ago, Superdad said:

Yeah, I've been wondering that for weeks now since John starting playing with this during measurement sessions.  Probably has something to do with regulatory requirements.

So to use John's grounding technique, does this mean we now need two outlets for each SMPS (unless grounding multiple SMPS from the same wire)?  I'm impossibly dense about electrical things.

[Ryelands]

44 minutes ago, mansr said:

Sorry if I misunderstood you.

No problem but thanks anyway. As I quoted John from memory, I may not have got his point quite right. My point OTOH is that he's to blame for all this.