USB Ground Lift

[Cornan]

I wouldn't know how to measure ground voltage, I'm a bit of an unqualified chancer when it comes to electronics.

 

;-)

 

The sound is considerably fuller, richer and more 3D. It was excellent before but somewhat less luscious. I had done experimenting before with ground lift when I had a Regen to positive effect. Then moving to Intona and W4S Recovery introduced more boxes and were both sensitive to compatibility (both had to have manufacturer revisions to work even with the 4 USB rails connected).

 

SQ now is borderline ridiculous and I can't really see what could be significantly improved from here.

 

I had been thinking about making a switched USB cable for some time (I even asked Curious to make one but he didn't see the merit in it) as I had a hunch that ground was needed for handshake but maybe not for data transfer, otherwise it wouldn't explain why the Regen worked without ground. I know that previously my mains was providing an earth path, but upgrading to Swagman Labs SE LPS's provided mains ground isolation, meaning that I had to re-ground my USB cables. I tried one yesterday and was impressed and this morning I removed my Curious Link and put another DIY switched cable in, thus removing ground from the entire USB chain.

 

My guess is that 'the crap' uses ground to travel?

 

I am all with you r_w! I have used external grounding (Entreq grounding boxes) for several years to clean the ground from noises/crap with great results. Especially good results for USB audio (digital chain) in my experiance...but also very awarding in the analogue side (just important to keep digital and analogue separated with external grounding). Ground is the return path of noises as well. Ensuring a good ground connection and making sure to avoid ground loops is extremely awarding.

Personally I cannot listen to music without external grounding anymore. Everytime I try without it the music becomes dull in comparison. My next mission is dedicated mains, a proper star ground and unshielded 2-wire USB cables (& XLR headphone cables) which I am absolutely sure is the way to go. I'll just need to figure everything out before I make it real!

 

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[Cornan]

I have tried a USB cable with the +5v and GND removed.

It did not work and I agree with mmerrill99 that you need to have the GND.

 

I finally settled on a split USB cable (Dual head) which I would recommend.

The sound had a much better foundation with a sense of solidity in the sound stage.

The cable with only the +5v removed sounds a little thinner in comparison.

 

 

AFAIK there are no Y-split USB cables without shielding around. They are not made to be disconnected from 5v but to be connected to USB power (5v BPS or LPS). If you dissconnect a Y-split cable you will for sure experiance a ground loop running through the shields and/or dielectric materials. It could potensially harm the connected device as well. Several Regens have been reported damaged this way according to Superdad.

If you want to disconnect the power and GND unshielded cables is your only option...and without a star ground a 2-wire USB cable will not work properly.

 

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[Cornan]

Here is a very good thread to read for more info regarding USB ground http://www.computeraudiophile.com/f10-music-servers/vbus-isolator-sbooster-26228/

Read both John Swenson and Karin's (SBooster) replies.

 

Ps. Note r_w's posts there as well! Ds.

[Cornan]

Elijah Audio can actually make this cable that works with any setup.

However, I agree with r_w that there should be a ground lift switch on DAC's USB inputs or atleast a "VBus Isolator type of USB adapter" with a ground switch. It will not work for everyone...but will be a sound revolution for many!

 

 

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[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

 

 

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[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]

[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.

 

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[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!

[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!

 

 

 

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[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.

 

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[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.

 

 

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[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?

[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.

[Cornan]

Sorry Cornan, I don't think that is correct. All USB hubs must connect their input to a USB host ('A' jack). So while a lot of them have a--typically short--captive input cable with a male 'A' plug to do so, all desktop USB hubs that do not have a captive cable have a female USB 'B' jack. Thus one uses a standard USB A>B cable to connect a hub to a computer. We of course adhered to that standard with the REGEN ('B' in, 'A' out), though for best signal integrity and impedance match we advise putting the hub (REGEN) as close to the DAC as possible.

 

Ciao,

 

--Alex C.

Hi Alex!

Here is a Google search for "normal" USB hubs https://www.google.se/search?q=usb+hub&client=tablet-android-google&prmd=isvn&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjJmcr21tXOAhUEDCwKHek1BLoQ_AUIBygB&biw=600&bih=960

Sorry, but I cannot find a single hub with female USB B jacks...just female USB A jacks and male A plugs.

:-)

 

My point with this was that Corning requires power via the USB B plug...and my guess is if a hub was used it was inserted to the A side of the Corning which will not work according to Corning's FAQ.

 

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[Cornan]

It is true that most hubs these days have captive input cords (with male 'A' plugs), but you will NEVER see the input of a hub be a female 'A' jack--those are for the devices only. Small hubs used to come with 'B' jack inputs until the captive-cord craze. Nowadays it is mostly just the hubs with quite a few ports that have an input jack.

 

Here are a few I found quickly on Amazon:

https://www.amazon.com/Rosewill-7-Port-Power-Adapter-RHUB-300/dp/B004F38VFO

https://www.amazon.com/AmazonBasics-Port-USB-Power-Adapter/dp/B00DQFGJR4

https://www.amazon.com/USB-Highspeed-Port-Adapter-Silver/dp/B002FFZGCU

Thanks Alex! I actually have'nt seen those around...but have'nt really looked them up either. This type of hub could work for the Corning...even if I personally would'nt use them in an audio chain. USB Regen is a much much better choise!

 

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[Cornan]

Well, wouldn't that be because the Intona itself already disconnects the GND?

 

+1. However, benefits could be made if the modded Supra USB cable/adapter was BEFORE the intona instead of after. Also very important to make sure that the ground wire + shield to ground connection (if any) is properly removed.

[Cornan]

You have to have the ground for handshake.

 

That is why the GND have to be removable after the handshake is done. It have to have a switch or DC male+female plugs on the GND wire to work at all.

[Cornan]

Did you read my post???

I can disconnect the ground. It doesn't make one bit of difference in SQ disconnected or connected.

 

My theory: The Intona is doing it's job, I have galvanic isolation, no ground loop. All other components including DAC, 5V vbus (eliminated) and Regen are also properly isolated from introduction of any ground loops. Thus the disconnecting of the USB ground is unnecessary.

 

In fact, if you are hearing a difference when disconnecting the USB ground after handshake, you have a ground problem with one of your devices or 5V vbus.

 

I read it but did'nt get the impression that you actually connected & disconnected the GND. Sorry if I missunderstood.

As long as you have another USB cable with GND you will not hear the full potensial IMO. I am lifting the GND on all of my USB cables (plus no shielding) in the chain. All GND lifts makes a difference for the better...even if the first one gives the best SQ result. Intona will isolate the output no the next device..but you still need to mind about the other USB paths. Ground loops is not the only noise you have to care about. Grounds carry a lot of other noises. Anyway, I do not wish to start yet another GND lift or not discussion. It is all up to you if you are curious enough to give it a try. I am just showing you my side of the coin!

 

 

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[Cornan]

Sorry I can't give a real opinion on IFI'S I DEFENDER. My headphones went back to Mr Speakers for the flow upgrade the day i got the IFI ....... works nice as a port for battery 5v. Hard to say with thier iso lift and my hack 5v cable compare without any form of GND lift on mine.. ..

I will push to say yes better but no review for a while...3 weeks and 200 hours headphone burn in. + Need to make a manual 5v GND lift USB cable.....

Making it worse I just had a new electric meter fitted and a balanced isolation transformer coming...

Dam you Cornan .... you Svenske temptress....

 

 

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*Haha* there is a lot of temptations around this community!

I actually knew about the Isolation transformers a long time ago through @zilch0md when nobody else was discussing this matter. He described everything very clear and detailed (as he normally does). I just was'nt ready for the news at the time and honestly found those IT's ugly looking. If I would have taken his advice then I would most likely be in a better position now.

Temptations, knowledge and WAF needs to sync. I just needed some more temptation from JS and time to find a IT that had everything I'll need and was small enough to hide!

Well, money is always another disturbing factory's as well!

 

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[Cornan]

2 hours ago, marce said:

Entreq boxes are floating...

 

Did you realize that this was a post from over two years ago? ?

[Cornan]

3 hours ago, beerandmusic said:

i had to look myself...i was thinking how is this even relavent with all the usb toys on the market...then i noticed timestamp.

 

Yeah its an old post. However there is still some truth in it. Battery supplies do improve SQ when a Entreq Minimus grounding box is attached to the -Ve of the battery output. Let me get this straight that this have probably nothing to do about grounds or 0v reference. Probably more about static electricity and/or EMI or even high impedance leakage. I don’t really know. It is just a guess based on other experiments in the field. All I know is that it 100% improve SQ.

 

A grounding box can have a very positive impact on the shield ground on USB cables. At the time of my original post back in 2016 I thought it might be positive to GND of the USB cable, but it is not. It is soley positive to the shield.

[Cornan]

7 hours ago, rikhav said:

I made my current USB cable into a dual headed USB cable with the help of my friend

One connector has the Data + and - connections and other Voltage and its ground

 

But the moment i remove the connector carrying voltage my DAC is disconnected from windows.

So does that mean my DAC needs constant voltage even after hand shake?

 

My DAC is a Burson Conductor having a C-Media USB interface

 

Or is it that i just have to disconnect the voltage ground, but even doing that will make the circuit incomplete

I am a little confused so want help from members who have tried this trick

 

Will it be a good idea to connect the second USB connector carrying voltage and its ground to a linear power supply ?

 

Lastly with this modification is a USB regenerator / reclocker like Uptone / W4S recovery advised to be used between PC and DAC?

 

TIA

 

Yes, it could mean that your DAC needs to see a 5v feed. You can possibly still do a USB ground lift, but for that to work the 5v lead needs to be attached at all time and the GND lead needs to have its own detatchable connection (for example a DC male plug and a DC female plug). When the DAC have started you can unplug the GND (but keave the 5v connected). This might work IF your DAC does’nt require GND as well. To find out you’ll need to do a little research among other users of your perticular DAC or just make your own experiment to see if it works or not.

 

Furthermore some DACs need to have the 5v and GND removed in a certain sequence. Starting with removing GND and then 5v (or the other way around. My memory fails me). I have no idea if your DAC is one of those though.

 

It is always a good idea to provide clean power to the USB so a LPSU is a wise choise as well as using a ISO Regen or similar USB re-generators on top of that (powered with clean power). Mind you that ISO Regen needs to see 5v as well.

[Cornan]

48 minutes ago, rikhav said:

Tried connecting voltage + and - to an LPSU but still DAC is not detected

Need to connect the USB header having voltage + and - to PC , then only DAC gets detected 

 

Not sure what to make of this

Sounds to me that you have a ground loop since it is working with just 5v but not 5v+GND connected to a LPSU. Draw a simple diagram of your system ground connections (AC/DC/IC) and post it here in order for me (or anyone else) to help you.