USB Ground Lift

[r_w]

Thanks for that info John,

 

I have a battery operated meter, where/how can I take this measurement to find if there is 50 or any voltage getting to the DAC?

 

Thanks v much in advance.

 

It sounds so bloody good, I would hate to reconnect ground unless utterly essential.

 

;-)

 

 

Hi all,

this is a topic of intense research right now, some proper solutions for this will (hopefully) be coming out soon.

 

If you have been following some of my posts recently a lot of what seems to be related to the last significant chunk of SQ problems seems to be related to power supply leakage current ( see some of my other posts for descriptions of what this is) forming ground loops through various parts of the audio system.

 

The leakage current from the computer seems to be a major part of this in many systems (note: not all), the loop frequently flows through the ground of the USB cable hence blocking the ground in the USB cable CAN make things much better.

 

But not always. I'm working with one person whose system got much worse when the USB ground was blocked, the loop wound up going through the preamp instead which made it much worse sounding.

 

On USB and grounding in general, a device will not connect to a host unless there is a ground, both from SE0 and the pull up resistors that signal connection and bus speed. It is true that after the connection is established the ground is not actually needed for many USB transceivers, BUT there are some big issues with doing that.

 

Two truly ground isolated systems can develop a LOT of voltage between them, primarily from the above mentioned leakage current from the power supplies. It exists for ALL power supplies, even LPS, but SMPS is usually worse. I did some measurements on some systems around my house and found around 50V on most isolated systems I setup.

 

This means that if you setup a computer feeding a DAC with a USB cable with all grounds cut and there is no other ground connections between them, the ground between those two systems will probably have around 50V between them. This means the DAC's USB chip is going to be seeing 50V on its pins, this is NOT a good thing!!!! The fact that a DAC still runs at all under these conditions is due to ESD protection circuits designed to protect against "static" discharges, unfortunately these circuits are only designed to be used for very short duration events, not continuous large DC offsets. They are protecting the USB receiver from being fried, but they will not continue to do so for a long time. Eventually they will fail and PFFT! your DAC goes up in smoke.

 

There are some proper solutions being worked on right now do deal with these issues, leakage current, ground loops in general etc, and in particular with regards to USB.

 

If you want to experiment with USB ground isolation techniques be aware that you might be risking damaging your equipment, only you can decide if the SQ improvements are worth the risk. If you do have significant voltage difference between grounds the failure of the ESD protection circuits may happen in a couple weeks, 6 months, or maybe even as long as a year, but it will eventually happen.

 

How do you measure it? You need a battery operated meter (or scope) that has a decent bandwidth on its AC setting. This voltage is AC, not DC, so use an AC range. Do not use a meter or scope that plugs into the wall, this will generate its OWN leakage current which will completely mess up anything you are trying to measure. I personally use a scope with a differential probe run off batteries.

 

John S.

[Cornan]

Hi all,

this is a topic of intense research right now, some proper solutions for this will (hopefully) be coming out soon.

 

If you have been following some of my posts recently a lot of what seems to be related to the last significant chunk of SQ problems seems to be related to power supply leakage current ( see some of my other posts for descriptions of what this is) forming ground loops through various parts of the audio system.

 

The leakage current from the computer seems to be a major part of this in many systems (note: not all), the loop frequently flows through the ground of the USB cable hence blocking the ground in the USB cable CAN make things much better.

 

But not always. I'm working with one person whose system got much worse when the USB ground was blocked, the loop wound up going through the preamp instead which made it much worse sounding.

 

On USB and grounding in general, a device will not connect to a host unless there is a ground, both from SE0 and the pull up resistors that signal connection and bus speed. It is true that after the connection is established the ground is not actually needed for many USB transceivers, BUT there are some big issues with doing that.

 

Two truly ground isolated systems can develop a LOT of voltage between them, primarily from the above mentioned leakage current from the power supplies. It exists for ALL power supplies, even LPS, but SMPS is usually worse. I did some measurements on some systems around my house and found around 50V on most isolated systems I setup.

 

This means that if you setup a computer feeding a DAC with a USB cable with all grounds cut and there is no other ground connections between them, the ground between those two systems will probably have around 50V between them. This means the DAC's USB chip is going to be seeing 50V on its pins, this is NOT a good thing!!!! The fact that a DAC still runs at all under these conditions is due to ESD protection circuits designed to protect against "static" discharges, unfortunately these circuits are only designed to be used for very short duration events, not continuous large DC offsets. They are protecting the USB receiver from being fried, but they will not continue to do so for a long time. Eventually they will fail and PFFT! your DAC goes up in smoke.

 

There are some proper solutions being worked on right now do deal with these issues, leakage current, ground loops in general etc, and in particular with regards to USB.

 

If you want to experiment with USB ground isolation techniques be aware that you might be risking damaging your equipment, only you can decide if the SQ improvements are worth the risk. If you do have significant voltage difference between grounds the failure of the ESD protection circuits may happen in a couple weeks, 6 months, or maybe even as long as a year, but it will eventually happen.

 

How do you measure it? You need a battery operated meter (or scope) that has a decent bandwidth on its AC setting. This voltage is AC, not DC, so use an AC range. Do not use a meter or scope that plugs into the wall, this will generate its OWN leakage current which will completely mess up anything you are trying to measure. I personally use a scope with a differential probe run off batteries.

 

John S.

 

Thanks a lot John!

I have just two questions. AFAIK the use of a star ground would solve the issue with high voltage between the USB source (computer/streamer) and the DAC since it will provide an "ultimate" path to ground on each device. Am I right in this assumption?

Also, you mensioned LPS and SMPS only. Would'nt BPS be the best option since it should have less leakage current if disconnected from mains (disregarding the coming LPS-1 or Ultracaps)?

I personally prefer BPS to LPS but have'nt on the other hand tried any LPS above the $400 mark.

 

/Micael

 

 

Sent from my Nexus 7 using Computer Audiophile mobile app

[sandyk]

I suspect that the 50V quoted by John may be considerably higher in 230V AC 50HZ countries .?

[Cornan]

I suspect that the 50V quoted by John may be considerably higher in 230V AC 50HZ countries .?

 

Good question Alex! I for one would be interested to know the answer to that question. I wonder if it really could be close 100v in Sweden with 240v 50Hz? [emoji15]

[JohnSwenson]

You want to measure across the switch you put in to the cable, ie between the computer ground and the DAC ground with the switch open. Measure both DC and AC, the DC should be small, the AC might be large. It can be anywhere you can get to the ground. Make sure the point is actually connected to the ground that you are breaking with the switch.

 

John S.

 

Thanks for that info John,

 

I have a battery operated meter, where/how can I take this measurement to find if there is 50 or any voltage getting to the DAC?

 

Thanks v much in advance.

 

It sounds so bloody good, I would hate to reconnect ground unless utterly essential.

 

;-)

[JohnSwenson]

Thanks a lot John!

I have just two questions. AFAIK the use of a star ground would solve the issue with high voltage between the USB source (computer/streamer) and the DAC since it will provide an "ultimate" path to ground on each device. Am I right in this assumption?

Also, you mensioned LPS and SMPS only. Would'nt BPS be the best option since it should have less leakage current if disconnected from mains (disregarding the coming LPS-1 or Ultracaps)?

I personally prefer BPS to LPS but have'nt on the other hand tried any LPS above the $400 mark.

 

/Micael

 

 

Sent from my Nexus 7 using Computer Audiophile mobile app

If by a star ground you mean a common point that all safety grounds are connected to, this will only provide what you are thinking of IF ALL boxes have a safety ground and that is connected to the negative output of every power supply in the system. The moment you have ANY two pronged PS or something whose negative DC rail is NOT connected to that star ground point you can develop significant voltage due to leakage current.

 

It's kind of an all or nothing thing. For best results either every "ground" point (chassis, shell of RCA jack, shield of digital cable etc) should be connected together with very low impedance wires, OR there should be no connections from negative PS in one box to another. In the first case the leakage currents from the PSes will be flowing through such low impedances they will not generate much voltage, OR the other extreme generates large voltages but nobody cares.

 

Every real system is somewhere in between.

 

John S.

[sandyk]

The moment you have ANY two pronged PS or something whose negative DC rail is NOT connected to that star ground point you can develop significant voltage due to leakage current.

 

An exception will of course be John's own JS2 Linear PSU !!!

[Cornan]

If by a star ground you mean a common point that all safety grounds are connected to, this will only provide what you are thinking of IF ALL boxes have a safety ground and that is connected to the negative output of every power supply in the system. The moment you have ANY two pronged PS or something whose negative DC rail is NOT connected to that star ground point you can develop significant voltage due to leakage current.

 

It's kind of an all or nothing thing. For best results either every "ground" point (chassis, shell of RCA jack, shield of digital cable etc) should be connected together with very low impedance wires, OR there should be no connections from negative PS in one box to another. In the first case the leakage currents from the PSes will be flowing through such low impedances they will not generate much voltage, OR the other extreme generates large voltages but nobody cares.

 

Every real system is somewhere in between.

 

John S.

 

Thanks John!

For now I am leaning towards using this type of RF star router:

I will connect it with very low impedance wires to the chassi of all my devices (including Regen) and ground it to a Entreq Tellus grounding box. I will use unshielded 2-wire USB cables and XLR's between the devices.

My battery supplies (2pcs) will be grounded as well.

I will just send a pm to Entreq for further advices before I perform the "tweak". I'll need to make 100% sure that it will be safe before I make the switch.

 

Sent from my Nexus 7 using Computer Audiophile mobile app

[r_w]

Hi John,

 

I've tried a few points with my battery multimeter, set to smallest voltage setting (200ma), there is circa 0.15 AC voltage and 0 DC voltage.

 

I tried lots of methods of comparing the USB cable with itself and other earth points in the setup. However, I will try a few more earth points to be absolutely sure, but it appears on first check that there is very little or no erroneous ground voltage. Am I doing this wrong?

 

My source setup is a star earthed 8 way metal IEC block being fed from an AC>DC : DC>AC regenerator (fed from dedicated mains distribution board), Also the digital source is an Aurender Server (LPS), not a standard computer, so there is no SMPS in the digital chain... is it possible that this is helping?

 

Thanks for your advice by the way, it's much appreciated.

 

Thanks in advance : Ron

 

You want to measure across the switch you put in to the cable, ie between the computer ground and the DAC ground with the switch open. Measure both DC and AC, the DC should be small, the AC might be large. It can be anywhere you can get to the ground. Make sure the point is actually connected to the ground that you are breaking with the switch.

 

John S.

[r_w]

Scratch my previous results... I didn't have the multimeter probes in the correct sockets.

 

Now I measure, everywhere along the USB chain I've tested at : DC 0.3 Volts and AC 1.06 Volts.

 

Does that sound right?

 

Thanks in advance

 

 

Hi John,

 

I've tried a few points with my battery multimeter, set to smallest voltage setting (200ma), there is circa 0.15 AC voltage and 0 DC voltage.

 

I tried lots of methods of comparing the USB cable with itself and other earth points in the setup. However, I will try a few more earth points to be absolutely sure, but it appears on first check that there is very little or no erroneous ground voltage. Am I doing this wrong?

 

My source setup is a star earthed 8 way metal IEC block being fed from an AC>DC : DC>AC regenerator (fed from dedicated mains distribution board), Also the digital source is an Aurender Server (LPS), not a standard computer, so there is no SMPS in the digital chain... is it possible that this is helping?

 

Thanks for your advice by the way, it's much appreciated.

 

Thanks in advance : Ron

[Cornan]

Here is a good link regarding audio system grounding if someone is interested to dig deeper in the subject Audio System Grounding And Troubleshooting | Core Audio Technology. Just disregard the slightly "angled" touch and do not forget to watch the video. Very useful IMO!

[r_w]

Bump...

 

Just curious to know if these measurements are good / make sense?

 

TIA

 

Scratch my previous results... I didn't have the multimeter probes in the correct sockets.

 

Now I measure, everywhere along the USB chain I've tested at : DC 0.3 Volts and AC 1.06 Volts.

 

Does that sound right?

 

Thanks in advance

[sandyk]

r_w

 

Looks pretty good to me.

 

Regards

Alex

[Cornan]

I have finally pulled the plug! I descided to cut the GND wire on my K-Lite 500 and added a female & male Dc 2,1mm plugs (no solder). My Entreq Minimus is externally grounding my Pioneer U-05 plus my Aries Mini (powered by battery). After the initial handshake/hello everything works great and sounds just amazing. I am a very happy camper!

 

 

 

Sent from my Nexus 7 using Computer Audiophile mobile app

[JohnSwenson]

Bump...

 

Just curious to know if these measurements are good / make sense?

 

TIA

 

Those numbers are low enough that you are not in danger of frying anything. You probably have a connection between boxes through the USB transceivers which is limiting the voltage. That is a good thing.

 

John S.

[r_w]

Thanks.

 

Those numbers are low enough that you are not in danger of frying anything. You probably have a connection between boxes through the USB transceivers which is limiting the voltage. That is a good thing.

 

John S.

[Le Concombre Masqué]

I have a Corning cable and a Uptone Regen. The Corning is very unstable even on a properly configured 3.0 port. It seems though I can get it to connect to my 5V requiring DAC (TEAC 501 ) with 100% chance of success when I plug in parallel another cable in the headphone output of my Mac AND in the very same preamplifier to which the DAC is XLR connected.

 

Only rational seems that the Corning gets a ground feedback via the second cable connected to the pre connected to the DAC...

 

Any idea of a better solution than running 2 cables ? replace the Regen by a mere hub ??

[Cornan]

I have a Corning cable and a Uptone Regen. The Corning is very unstable even on a properly configured 3.0 port. It seems though I can get it to connect to my 5V requiring DAC (TEAC 501 ) with 100% chance of success when I plug in parallel another cable in the headphone output of my Mac AND in the very same preamplifier to which the DAC is XLR connected.

 

Only rational seems that the Corning gets a ground feedback via the second cable connected to the pre connected to the DAC...

 

Any idea of a better solution than running 2 cables ? replace the Regen by a mere hub ??

 

Yes, it do sounds like a DAC handshake problem to me. Have you tried to remove the second cable when the music have started? If it works your Corning cable somehow does'nt provide the GND connection required for the handshake. I personally remove my GND myself after handshake and it sounds better.

However, please look at JS answers to r_w to understand how to measure ground currents to ensure safety.

 

Sent from my Nexus 7 using Computer Audiophile mobile app

[Le Concombre Masqué]

Every time I pull the jack cable, the Corning stops working. And it works with the Regen but not with a hub

Yes, it do sounds like a DAC handshake problem to me. Have you tried to remove the second cable when the music have started? If it works your Corning cable somehow does'nt provide the GND connection required for the handshake. I personally remove my GND myself after handshake and it sounds better.

However, please look at JS answers to r_w to understand how to measure ground currents to ensure safety.

 

Sent from my Nexus 7 using Computer Audiophile mobile app

[Cornan]

Every time I pull the jack cable, the Corning stops working. And it works with the Regen but not with a hub

Do you mean that the Corning works with Regen but not with a normal hub? Is the normal hub powered by a psu or USB powered? Since your DAC require 5v the hub needs to be powered by a psu to work (like Regen). Not all DAC's will work without GND either. Since that Corning cable is pretty special I suggest you ask the manufacturer about it.

If you explain your complete audio chain (ex. Mac>Corning>Regen>DAC etc) it will be easier for anyone to understand possible causes.

 

 

Sent from my Nexus 7 using Computer Audiophile mobile app

[Le Concombre Masqué]

thank you. Prior to the Regen I had that hub and it worked but was very unstable. Most probably if I had spent time plugging/unplugging the Corning the powered hub would have worked in the end as it has already worked and as the Regen works without the second cable when I spend time plugging/unplugging the Corning till they hook.

 

The extraordinary thing is that I get 100 % fast (2/3 seconds) hooking with the Regen and the second cable.

 

Chains are : MacbookPro >Corning>unboxed Green Regen card>DAC > Jeff Rowland pre via Cardas XLR

Mac>cheap jack cable out of the headphones output >Jeff Rowland pre

[Cornan]

thank you. Prior to the Regen I had that hub and it worked but was very unstable. Most probably if I had spent time plugging/unplugging the Corning the powered hub would have worked in the end as it has already worked and as the Regen works without the second cable when I spend time plugging/unplugging the Corning till they hook.

 

The extraordinary thing is that I get 100 % fast (2/3 seconds) hooking with the Regen and the second cable.

 

Chains are : MacbookPro >Corning>unboxed Green Regen card>DAC > Jeff Rowland pre via Cardas XLR

Mac>cheap jack cable out of the headphones output >Jeff Rowland pre

 

AFAIK no "normal" USB Hubs have USB B inputs...just with USB A plugs. Here is a FAQ from Cornings website:

I want to charge my portable device (like iPhone or iPad) with USB 3.Optical™ Cables by Corning. Is that possible?

USB 3.Optical Cables by Corning are designed to be used with self-powered peripherals only. No significant power is available after powering its internal opto-electronics. A self-powered USB 3.0/2.0 hub can always be used at the peripheral (B-side) to provide power if desired.

Here is some more FAQ´s Customer Service | Optical Cables by Corning

Maybe a clue!? :-)

[Cornan]

The reason for it to work quicker with additional cable could be due to the optical construction of the USB cable. Regen is AFAIK just "forwarding" the GND handshake from the source. The GND signal might be "weaker" due to the optical construction and speeds up by additional GND path. This might also suggest a ground loop since you likely have multiple paths to ground.

 

Interesting to know is also how you are powering your unboxed Regen? Battery, LPS or SMPS?

[Le Concombre Masqué]

MeanWell smps

 

how Can a ground loop issue prevent a gnd connection ? it happens the same whether the laptop is plugged or on its battery

The reason for it to work quicker with additional cable could be due to the optical construction of the USB cable. Regen is AFAIK just "forwarding" the GND handshake from the source. The GND signal might be "weaker" due to the optical construction and speeds up by additional GND path. This might also suggest a ground loop since you likely have multiple paths to ground.

 

Interesting to know is also how you are powering your unboxed Regen? Battery, LPS or SMPS?

[Cornan]

MeanWell smps

 

how Can a ground loop issue prevent a gnd connection ? it happens the same whether the laptop is plugged or on its battery

 

That is not what I ment. A ground loop does´nt prevent a GND connection. However, when you insert an additional cable you might end up with a ground loop (depending on were the other end of this cable is connected).

If I were you I would check with another USB cable and see if you get the same results. If not it could be due to the optical construction.