SMPS and grounding

[sandyk]

14 hours ago, Cornan said:

A isolation transformer, even one with floating secondary, have the safety ground intact. It is just the output that is not grounded to the secondary of the isolation transformer.

 

 

 It takes something like 50mA of A.C. to kill you.

That is unlikely to be noticed by an RCD on the Primary side when the output is far, far, greater than that amount of current ?

Just because the AC output is floating, doesn't mean that devices powered by it don't have any return path to earth.

Please correct me if my thinking in this area is incorrect.

One and a half is the resident expert in this area.

 

Alex 

[One and a half]

5 hours ago, jamesg11 said:

/& so safety cut-out required downstream of secondary ...

In fairness, Cornan's drawing doesn't show any protection systems.

 

The whole idea of grounding one of the secondaries is for safety, the other(s) are:

- Common mode noise is not introduced again. 

- Floating the neutral creates a voltage between earth and the neutral which equipment may not be appreciative of

 

Here's a white paper from Powervar explaining the causes of neutral to earth voltages of interest.

Their ground guard device is an isolation transformer, so common mode noise is knocked on the head, and one secondary is tied to ground (earth). This keeps the voltage of the neutral very close to ground, but , and but again, does not cause current to flow in the ground, the return current goes to the transformer where it originated.

 

 

- 

Powervar Neutral to Ground Voltage causes and cures wp202.pdf

[Cornan]

6 hours ago, sandyk said:

 

 It takes something like 50mA of A.C. to kill you.

That is unlikely to be noticed by an RCD on the Primary side when the output is far, far, greater than that amount of current ?

Just because the AC output is floating, doesn't mean that devices powered by it don't have any return path to earth.

Please correct me if my thinking in this area is incorrect.

One and a half is the resident expert in this area.

 

Alex 

 

I was only anwering the question from @flkin. He never asked for any advices regarding safety. Since he already own a isolation transformer with floating secondary I assume he already knows about this or ask about it.

 

A RCD/GFCI should always be used at the output of a isolation transformer with floating secondary. As @One and a half have kindly explained to me before a balanced isolation transformer needs a 2-pole RCD/GFCI. These can be pretty hard to find if you are looking for a portable one, so here is a 240v Schuko plug one that I have ordered for my balanced isolation transformer with floating secondary. I will receive two today and will use one the output of my isolation transformer with floating secondary (replacing my 1-pole ditto) and on the output of my balanced isolation transformer with floating center tap.

 

https://www.brennenstuhl.com/de-DE/personenschutz-adapter-bdi-a-2-30-ip54

 

 

Another thing. Do not feel totally safe even with a RCD/GFCI at the output of a IT. A RCD/GFCI should be regulary checked to ensure functionallity.  

 

[flkin]

3 hours ago, Cornan said:

 

I was only anwering the question from @flkin. He never asked for any advices regarding safety. Since he already own a isolation transformer with floating secondary I assume he already knows about this or ask about it.

 

A RCD/GFCI should always be used at the output of a isolation transformer with floating secondary. As @One and a half have kindly explained to me before a balanced isolation transformer needs a 2-pole RCD/GFCI. These can be pretty hard to find if you are looking for a portable one, so here is a 240v Schuko plug one that I have ordered for my balanced isolation transformer with floating secondary. I will receive two today and will use one the output of my isolation transformer with floating secondary (replacing my 1-pole ditto) and on the output of my balanced isolation transformer with floating center tap.

 

https://www.brennenstuhl.com/de-DE/personenschutz-adapter-bdi-a-2-30-ip54

 

 

Another thing. Do not feel totally safe even with a RCD/GFCI at the output of a IT. A RCD/GFCI should be regulary checked to ensure functionallity.  

 

 

Thanks for helping Cornan. I do have an Isolation Transformer with floating secondary today. And around Dec 2016 I believe it was either you or One and a Half that gave me instructions on how to wire it up. I eventually got an electrician to do so for my 230V system.

 

In my floating secondary, only the Neutral and Live wires are connected. The Neutral is attached to the chassis of the transformer. There is no Earth/Ground. On the primary side the Earth/Ground is attached to the chassis also.

@JohnSwenson says that the DC negative should be connected to the Earth/Ground where the SMPS is plugged in. In my case, I cant do that so does it mean I have to connect the DC negative out to the primary side Earth/Ground? I don’t see any other choice.

[Cornan]

20 minutes ago, flkin said:

 

Thanks for helping Cornan. I do have an Isolation Transformer with floating secondary today. And around Dec 2016 I believe it was either you or One and a Half that gave me instructions on how to wire it up. I eventually got an electrician to do so for my 230V system.

 

In my floating secondary, only the Neutral and Live wires are connected. The Neutral is attached to the chassis of the transformer. There is no Earth/Ground. On the primary side the Earth/Ground is attached to the chassis also.

@JohnSwenson says that the DC negative should be connected to the Earth/Ground where the SMPS is plugged in. In my case, I cant do that so does it mean I have to connect the DC negative out to the primary side Earth/Ground? I don’t see any other choice.

 

As One and a half explained the grounds will go back to where they orginally came from, ie. the Isolation transformer. The IT is your 0v reference where the SMPSs is connected to.

 

If you want to free up a socket with the help of a power splitter plug like this one.

 

You can also buy a grounding box if you feel adventurous. I have my SMPS powering my network devices to a Entreq Minimus. It sounds way better than connected to the safety ground. Just be careful not to cause any leakage loops into other devices. I had some problems myself when grouding the DC- output of the floating SMPS powering my ISO Regen. I had to ground it to the safety ground and keep the network devices grounded to the Minimus to get rid of the loop.

 

[Superdad]

9 hours ago, Cornan said:

I will receive two today and will use one the output of my isolation transformer with floating secondary (replacing my 1-pole ditto) and on the output of my balanced isolation transformer with floating center tap.

 

I assume you realize that by not connecting the center tap it is no longer a "balanced transformer."  A hamburger without the meat patty in the middle is just a bun... 

[Cornan]

 

1 hour ago, Superdad said:

I assume you realize that by not connecting the center tap it is no longer a "balanced transformer."  A hamburger without the meat patty in the middle is just a bun... 

 

Maybe I choose the wrong words for it? In any case, here is the schematics. I have added a toggle switch at the outside of the balanced IT which cut the the center-tap ground. Balanced and floating. ?

[Cornan]

This might help someone that, just like me, have searched for DC2.5/5.5mm plugs and sockets without success. These have seemed to only be available in the dimension DC2.1/5.5mm. Guess what? Now they have started to appear. I´ve just ordered them here:

 

https://hobbyking.com/en_us/2-5mm-dc-power-plug-with-screw-terminal-block-5pcs.html

https://hobbyking.com/en_us/2-5mm-dc-power-socket-with-screw-terminal-block-5pcs.html

 

 

 

[thyname]

3 minutes ago, Cornan said:

This might help someone that, just like me, have searched for DC2.5/5.5mm plugs and sockets without success. These have seemed to only be available in the dimension DC2.1/5.5mm. Guess what? Now they have started to appear. I´ve just ordered them here:

 

https://hobbyking.com/en_us/2-5mm-dc-power-plug-with-screw-terminal-block-5pcs.html

https://hobbyking.com/en_us/2-5mm-dc-power-socket-with-screw-terminal-block-5pcs.html

 

 

 

 

Good find!

 

So, if I get these, what else do I need to implement the trick? Just the plug?

[Cornan]

11 minutes ago, thyname said:

 

Good find!

 

So, if I get these, what else do I need to implement the trick? Just the plug?

 

You just need short wires between the + and - terminals of the plugs & socket, a long ground wire (long enough to reach the power strip where the SMPS in plugged into) from the - terminal to a normal AC mains plug where you connect the ground wire to the GND of the plug. Pretty straight forward and very well explained by John on the first post on this thread:

 

 

What ever you do. Be careful not to get it wrong!

 

 

 

[BigGuy]

2 hours ago, Cornan said:

 

You just need short wires between the + and - terminals of the plugs & socket, a long ground wire (long enough to reach the power strip where the SMPS in plugged into) from the - terminal to a normal AC mains plug where you connect the ground wire to the GND of the plug. Pretty straight forward and very well explained by John on the first post on this thread:

 

 

What ever you do. Be careful not to get it wrong!

 

 

 

REMINDER!  One of the screw connectors needs to be rotated 180deg so that the +'s and -'s line up.  When you do this, there will be quite an offset between the two connectors so I actually made an offset connecting wire to get them on same plane, e.g....

 

                    ________

                    |

       _______

 

I then used 3/4 inch shrink to make a neat package.

[Cornan]

28 minutes ago, BigGuy said:

REMINDER!  One of the screw connectors needs to be rotated 180deg so that the +'s and -'s line up.  When you do this, there will be quite an offset between the two connectors so I actually made an offset connecting wire to get them on same plane, e.g....

 

                    ________

                    |

       _______

 

I then used 3/4 inch shrink to make a neat package.

 

You cannot be too careful! ? Otherwise the + and the - are clearly noted on the top of the plugs & sockets. Ofcourse you can miss it. But you shouldn't! ?

 

[jamesg11]

11 hours ago, Cornan said:

This might help someone that, just like me, have searched for DC2.5/5.5mm plugs and sockets without success. These have seemed to only be available in the dimension DC2.1/5.5mm. Guess what? Now they have started to appear. I´ve just ordered them here:

 

https://hobbyking.com/en_us/2-5mm-dc-power-plug-with-screw-terminal-block-5pcs.html

https://hobbyking.com/en_us/2-5mm-dc-power-socket-with-screw-terminal-block-5pcs.html

 

 

 

But no 2.1x5.0mm plug! Western Digital must have procured the entire world supply.

 

/& typical website bad-misleading-time consuming search that throws up heaps of 5.5 subs for 5.whateva ...

[sandyk]

https://www.computeraudiophile.com/forums/topic/31877-iso-regen-listening-impressions-kicked-off-with-some-measurements/?page=32

 

[Theobetley]

On 9/19/2017 at 10:27 PM, JohnSwenson said:

Over the last month I have been performing extensive tests on leakage currents coming from SMPS power supplies. One of the most important results from this investigations is the makeup of this leakage current.

 

Previously my understanding was that leakage current was mainly a low frequency phenoninum, 60Hz, and its harmonics (60, 120, 180, 240 etc). My early investigations seemed to show that this was true with some high frequency components from the switching operation, but that this was fairly small in comparison to the whole. This turned out to be not true. It turns out that SMPS leakage is very hard to measure, it consists of some VERY high impedance components, on the order of 300 Mega ohms and some much lower impedance components.

 

None of the standard electronics test equipment will properly measure this, there impedance is simply too low and drastically changes the signal while trying to measure it. My only option was to build my own ultra high impedance differential probe (around 10 Giga ohms) so I can measure leakage current directly (rather than its affect on other equipment).

 

Because of this ultra high impedance it turns out leakage current can go all kinds of places you don't think about. It turns out to be extremely difficult to block using normal techniques, the blocking device has to have over a giga ohm to significantly attenuate it, this is VERY tough to achieve.

 

It turns out the best way to deal with this high impedance part is to shunt it around the audio equipment, there is a very easy way to do this, ground the negative output of the SMPS. It seems that even SMPS that include a ground pin don't actually use it for anything. This sounds too simple, but it actually works. PLEASE do not under any circumstances  attempt to modify an SMPS to do this, this is DEADLY, to NOT attempt!!!

 

Fortunately there is a real easy - inexpensive way to do this, it doesn't take any complex knowledge, I'm calling this the power supply grounding adapter, here are a couple pictures:

 

 

This consists of three items and some wire. The yellow item is a three pin AC power plug (shown is the US model), the black parts are male and female DC barrel connectors with screw connectors, no soldering necessary! Amazon has a whole bunch of places selling these for CCTV cameras. The spec is 5.5mm outside and 2.1mm inside. Most you will see will be this spec. The + of the male is wired to the + of the female and - on the male goes to - of the female. Look at the close up picture, in order for the wire to go straight across one of the connectors has to be upside down. This is extremely important to get right. You can use many different types of wire for this, I used solid core 14AWG wire with the insulation stripped off.

 

A green wire goes from the ground pin of the AC plug to the - pin of one of the connectors, strip a little off and just stick it in with the wire going between the two connectors, use a screwdriver to tighten the screws, you are done.

 

The green wire does NOT have to be a heavy duty high power wire. The SMPS are already designed to be double insulated so the AC cannot show up on the DC output, grounding it does not pose any electrical threat. I just used some nice silicon rubber wire I bought on Amazon, but really any green wire will do.

 

You plug the output of the SMPS into the "jack" side, and the "plug" side goes into where you would have plugged the SMPS. The AC plug goes into the SAME power strip or duplex outlet where you plugged in the SMPS. This is very important to properly shunt the high impedance part of the leakage current. If it goes into a different circuit you can wind up making it worse.

 

You should do this on every SMPS that is somehow electrically connected into your sound system. Some items may have different connectors such and Ethernet switches etc. There are a bunch of different adapters available that can convert the 5.5/2.1 to just about anything out there, you may need to use a pair of these.

 

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:

 

 

 

That is a significant reduction in leakage for a $10 shunt adapter.

 

If you want to get it all you will have to use something like the LPS-1 which will get rid of it all.

 

Have fun,

 

John S.

 

I am always anxious to try a new tweak. This one however had me skeptical. I have 2 docking stations to load my data files  both driven by a smps so I decided to try this. It took a while because Amazon initially sent me all male connectors. When I got that corrected (Amazon is good at correcting things like this) I hooked up the necessary wires  but when I stuck it in one of my docking stations power inputs  it would not fit ... too big. So I gave up for a while but then I checked out the other docking station and the fat connectors did fit. So I tried again and wow all my files sounded more natural. Better bass and a significant amount of air around upper frequency instrument sounds. Now I have to get the 5.1 mm male connectors to feed my other DS. 

 

Well done John! And thank you so much. 

[Theobetley]

On 9/19/2017 at 10:27 PM, JohnSwenson said:

Over the last month I have been performing extensive tests on leakage currents coming from SMPS power supplies. One of the most important results from this investigations is the makeup of this leakage current.

 

Previously my understanding was that leakage current was mainly a low frequency phenoninum, 60Hz, and its harmonics (60, 120, 180, 240 etc). My early investigations seemed to show that this was true with some high frequency components from the switching operation, but that this was fairly small in comparison to the whole. This turned out to be not true. It turns out that SMPS leakage is very hard to measure, it consists of some VERY high impedance components, on the order of 300 Mega ohms and some much lower impedance components.

 

None of the standard electronics test equipment will properly measure this, there impedance is simply too low and drastically changes the signal while trying to measure it. My only option was to build my own ultra high impedance differential probe (around 10 Giga ohms) so I can measure leakage current directly (rather than its affect on other equipment).

 

Because of this ultra high impedance it turns out leakage current can go all kinds of places you don't think about. It turns out to be extremely difficult to block using normal techniques, the blocking device has to have over a giga ohm to significantly attenuate it, this is VERY tough to achieve.

 

It turns out the best way to deal with this high impedance part is to shunt it around the audio equipment, there is a very easy way to do this, ground the negative output of the SMPS. It seems that even SMPS that include a ground pin don't actually use it for anything. This sounds too simple, but it actually works. PLEASE do not under any circumstances  attempt to modify an SMPS to do this, this is DEADLY, to NOT attempt!!!

 

Fortunately there is a real easy - inexpensive way to do this, it doesn't take any complex knowledge, I'm calling this the power supply grounding adapter, here are a couple pictures:

 

 

This consists of three items and some wire. The yellow item is a three pin AC power plug (shown is the US model), the black parts are male and female DC barrel connectors with screw connectors, no soldering necessary! Amazon has a whole bunch of places selling these for CCTV cameras. The spec is 5.5mm outside and 2.1mm inside. Most you will see will be this spec. The + of the male is wired to the + of the female and - on the male goes to - of the female. Look at the close up picture, in order for the wire to go straight across one of the connectors has to be upside down. This is extremely important to get right. You can use many different types of wire for this, I used solid core 14AWG wire with the insulation stripped off.

 

A green wire goes from the ground pin of the AC plug to the - pin of one of the connectors, strip a little off and just stick it in with the wire going between the two connectors, use a screwdriver to tighten the screws, you are done.

 

The green wire does NOT have to be a heavy duty high power wire. The SMPS are already designed to be double insulated so the AC cannot show up on the DC output, grounding it does not pose any electrical threat. I just used some nice silicon rubber wire I bought on Amazon, but really any green wire will do.

 

You plug the output of the SMPS into the "jack" side, and the "plug" side goes into where you would have plugged the SMPS. The AC plug goes into the SAME power strip or duplex outlet where you plugged in the SMPS. This is very important to properly shunt the high impedance part of the leakage current. If it goes into a different circuit you can wind up making it worse.

 

You should do this on every SMPS that is somehow electrically connected into your sound system. Some items may have different connectors such and Ethernet switches etc. There are a bunch of different adapters available that can convert the 5.5/2.1 to just about anything out there, you may need to use a pair of these.

 

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:

 

 

 

That is a significant reduction in leakage for a $10 shunt adapter.

 

If you want to get it all you will have to use something like the LPS-1 which will get rid of it all.

 

Have fun,

 

John S.

 

John am I reading your plots right? 

That’s 30 dB quieter for the smps grounding! No wonder it sounds so good.

[thyname]

Do we have to do this for every single SMPS we have to avoid any leakage in the circuit, or just for the device we want to "fix" (i.e. in my case the router and the switch)?

 

Anyone willing to do this for me? Willing to pay for the parts, shipping and labor. I am in USA (DC area). I am terribly scared of messing with many electric stuff due to an accident when I was little.

 

Thanks!

[Bruce Orr]

6 minutes ago, thyname said:

Do we have to do this for every single SMPS we have to avoid any leakage in the circuit, or just for the device we want to "fix" (i.e. in my case the router and the switch)?

 

Anyone willing to do this for me? Willing to pay for the parts, shipping and labor. I am in USA (DC area). I am terribly scared of messing with many electric stuff due to an accident when I was little.

 

Thanks!

I can do this for you. Need to know how long you need the ground wire from plug to device to be. 

[thyname]

3 minutes ago, Bruce Orr said:

I can do this for you. Need to know how long you need the ground wire from plug to device to be. 

 

You got mail!

[flkin]

Or you can simply use linear power supplies instead of SMPS and hey presto, no leakage current with generally accepted better sound ... 

[Superdad]

2 hours ago, flkin said:

Or you can simply use linear power supplies instead of SMPS and hey presto, no leakage current with generally accepted better sound ... 

 

Actually, linear supplies do also have leakage currents.  Just not nearly as much.

[flkin]

Interesting! I was under the impression that LPS doesn't have the high impedance leakage currents that requires grounding of the DC negative to shunt away. I was under the impression that this is only a phenomenon of SMPSs. 

 

What's the magnitude of difference between leakage currents from SMPS and LPS? Is it significant enough to be a concern and having to shunt it away also?

[JohnSwenson]

On 10/23/2017 at 9:33 AM, thyname said:

Do we have to do this for every single SMPS we have to avoid any leakage in the circuit, or just for the device we want to "fix" (i.e. in my case the router and the switch)?

 

Anyone willing to do this for me? Willing to pay for the parts, shipping and labor. I am in USA (DC area). I am terribly scared of messing with many electric stuff due to an accident when I was little.

 

Thanks!

LPS in general have primarily the lower impedance leakage.

 

The problem with using a linear supply is that the output may not be grounded. An ungrounded output will not shunt the high impedance leakage from other network devices when used with one of the named switches. (other switches don't block network leakage whether they are grounded or not.

 

Thus if using one of the named switches AND using an LPS you still need to ground the output, not to shunt high impedance leakage from the lps, but to shunt the high impedance leakage coming from other devices on the network.

 

John S.

[austinpop]

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...

[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.