SMPS and grounding

[Superdad]

10 hours ago, sot13 said:

Would it be preferable to use the DC shunt cable ONLY on the opticalModule's power supply?

I think you ought to skip the ground shunt on both of those FMCs. They are not benefiting either unit. 

[JohnSwenson]

10 hours ago, sot13 said:

@JohnSwenson please help me out here: I am going to implement the DC shunt cable in the following setup

The question is the following: would this setup, "destroy" the isolation (galvanic?) offered by the Fiber optic cable? Would it be preferable to use the DC shunt cable ONLY on the opticalModule's power supply? Thank you in advance!

Yes that completely destroys the optical isolation. The shunt is there to shunt high impedance leakage from SMPS over Ethernet cable. So in this case you would never need it on the TP-Link, since the optical prevents it from going downstream. You only need it on the OM IF it is powered from an SMPS.

 

John S.

[barrows]

9 minutes ago, JohnSwenson said:

Yes that completely destroys the optical isolation. The shunt is there to shunt high impedance leakage from SMPS over Ethernet cable. So in this case you would never need it on the TP-Link, since the optical prevents it from going downstream. You only need it on the OM IF it is powered from an SMPS.

 

John S.

What he said...  I power my oMdeluxe with a high performance linear power supply, with the output floating.  This is on the "dirty" side (server, router, switch, etc) of my components in my workroom.  By powering the (critical) sending oMdeluxe by a floating linear supply, it is also well isolated from the noise produced on the power line by the computer gears.  The the optical fiber runs to the audio system (Signature Rendu SEoptical).  I also use a noise reducing Sablon Ethernet cable for the critical copper run to the oMdeluxe to keep noise coming in on the cable down as much as possible.  Note that the Sablon Ethernet cables, despite having expensive Telegartner connectors, do not have their shields connected to the connector bodies, so they do not create a ground connection between Ethernet points (unlike many other cables made with metal body connectors).

[Ferluna]

On 9/25/2017 at 5:52 PM, 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.

I had a problem were my turntable chain would sometimes produce a buzzing/humming sound...

 

It was only when using the turntable, all other inputs did not produce any buzzing or hum...

 

I was using an ART DJ Pre II preamp and that small preamp has a green light (aside from the dreaded blue led...) That turn brighter as the music is louder... That green led would sometimes go full green even when the TT was not being used!...

 

So I somehow stumbled upon this post after reading about the iFi Groundhog...  I tried that whole "if you touch the device or cable and if the hum goes away, it's a missing ground..." and sure enough the hum would go away if I touched the ground cable or the interconnects , ... So I tried John Swenson's method thinking it would basically be the same thing as the iFi clamp cable... Only I attached the ground cable on the actual adapter and the buzzing went away!!! 

 

I had read that I could buy a "grounded" power supply for my ProJect TT, called "Power-it"... The theory being that since the TT, preamp, amp, sub all had floating ground... One of them needed a reference ground ... I tried this by switching the PS on the Art DJ to s 12vcd PS that had 3 prongs ... but that did nothing to fix the problem... I tried testing for continuity touching the ground prong on the IEC cable and the negative part of the barrel conector and there was no continuity... It was not grounded , that third prong is probably not connected to anything...

 

Doing what John did here seemed to make the difference!!

[GMG]

@JohnSwenson would connecting to ground the outer ring of an unused rca/bnc socket on a device that is powered by a smps have the same effect or is it essential to add the ground directly to the DC cable?

 

many thanks. 
 

@Superdad would you consider selling smps with the internal ground shunt with other voltages other then your standard 7.5v?

or can you advise where such smps can be obtained?

[JohnSwenson]

4 hours ago, GMG said:

@JohnSwenson would connecting to ground the outer ring of an unused rca/bnc socket on a device that is powered by a smps have the same effect or is it essential to add the ground directly to the DC cable?

 

many thanks. 
 

@Superdad would you consider selling smps with the internal ground shunt with other voltages other then your standard 7.5v?

or can you advise where such smps can be obtained?

IF the RCA shell is connected to the circuit "ground" then yes, grounding the shell of an unused socket should do the same thing.

 

John S.

[GMG]

Thanks @JohnSwenson I will check that with the manufacturer of my device (miniDSP shd studio)

would I be wrong to assume that most devices are most probably designed with the rca shells grounded?

 

that said, if the RCA shell is indeed connected to circuit ground wouldn’t connecting this rca to another component which already has a ground (say like a preamp or DAC) provide the needed ground? Or is it better to provide this ground earlier in the chain before the leakage passes through the components? 
 

many many thanks for your knowledge and dedication!

[JohnSwenson]

13 hours ago, GMG said:

Thanks @JohnSwenson I will check that with the manufacturer of my device (miniDSP shd studio)

would I be wrong to assume that most devices are most probably designed with the rca shells grounded?

 

that said, if the RCA shell is indeed connected to circuit ground wouldn’t connecting this rca to another component which already has a ground (say like a preamp or DAC) provide the needed ground? Or is it better to provide this ground earlier in the chain before the leakage passes through the components? 
 

many many thanks for your knowledge and dedication!

You definitely don't want the DAC being the shunt, that is what we are trying to prevent. Leakage current getting to the DAC increases clock jitter inside the DAC which doesn't just add a little hum, it modulates every sound going through the DAC.

 

John S.

[GMG]

Thanks John 😀