[BiggerHead]

well we seem to have some consensus that lifting grounds can be important.  I think it's a little funny to shrug it off except when there's an obvious hum.  Ground loops can certainly enable more than just obvious hums and I think those measurements mmerrill99 showed seem reasonable (we don't have any specific reason to say they're false either).  Surely there must be things between obvious and inaudible even for objectivists.  I don't know about how barely audible noise effects sound quality.  I'm pretty sure harmonic noise does.  IHarmonics define voice of instruments and probably environments too. It's also clear that an obvious enough noise (like airplane engines) will mask detailed cues.  Some of the wording sounds a bit colorful to me though.  We can leave that for the subjective side for now for all I care, but anyway, noise is a real thing, and it seems that noise leaking from ground loops to analog sides of DACs is a real thing.

 

[sonitus mirus]

  well we seem to have some consensus that lifting grounds can be important.  I think it's a little funny to shrug it off except when there's an obvious hum.  Ground loops can certainly enable more than just obvious hums and I think those measurements mmerrill99 showed seem reasonable (we don't have any specific reason to say they're false either).  Surely there must be things between obvious and inaudible even for objectivists.  I don't know about how barely audible noise effects sound quality.  I'm pretty sure harmonic noise does.  IHarmonics define voice of instruments and probably environments too. It's also clear that an obvious enough noise (like airplane engines) will mask detailed cues.  Some of the wording sounds a bit colorful to me though.  We can leave that for the subjective side for now for all I care, but anyway, noise is a real thing, and it seems that noise leaking from ground loops to analog sides of DACs is a real thing.

 
When talking strictly about a USB cable, what properties would create enough difference to matter?  Will the conductor material make a noticeable difference?  Is gold the solution?  What about the cross sectional area of the conductor?  Do I need something as thick as my thumb to make a difference?  Perhaps my USB cables require an exotic solder compound to open up the sound stage that is degraded by a ground loop?  How does a USB cable reduce or eliminate noise leaking from ground loops?
 
.

 

[ralphp@optonline]

   
How does a USB cable reduce or eliminate noise leaking from ground loops?

I was kind of wondering that myself being how ground loops are well known to be very difficult to fix. Now that would be news worthy if all those annoying, and up till now very troublesome, ground loops could be corrected just by changing a cable. Wow!
 
So why didn't someone think of this before? All that education, degrees and titles and all these forums on the internet and yet WE ARE IT - YES INDEED right here on this very thread we have collectively solved the vexing problem of ground loops in audio systems and who would have thought since the solution staring us right in the face all this time. Just change the cables! Absolutely brilliant! Dare I say it but could a trip to Stockholm be in our future?

 

[mmerrill99]

 
well we seem to have some consensus that lifting grounds can be important.  I think it's a little funny to shrug it off except when there's an obvious hum.  Ground loops can certainly enable more than just obvious hums and I think those measurements mmerrill99 showed seem reasonable (we don't have any specific reason to say they're false either).  Surely there must be things between obvious and inaudible even for objectivists.  I don't know about how barely audible noise effects sound quality.  I'm pretty sure harmonic noise does.  IHarmonics define voice of instruments and probably environments too. It's also clear that an obvious enough noise (like airplane engines) will mask detailed cues.  Some of the wording sounds a bit colorful to me though.  We can leave that for the subjective side for now for all I care, but anyway, noise is a real thing, and it seems that noise leaking from ground loops to analog sides of DACs is a real thing.

When talking strictly about a USB cable, what properties would create enough difference to matter?  Will the conductor material make a noticeable difference?  Is gold the solution?  What about the cross sectional area of the conductor?  Do I need something as thick as my thumb to make a difference?  Perhaps my USB cables require an exotic solder compound to open up the sound stage that is degraded by a ground loop?  How does a USB cable reduce or eliminate noise leaking from ground loops?

There are a couple of properties that matter:
- I've mentioned already that the structure & configuration of the shield matters - braid shields will shield a different spectrum to foil shields. The tightness of the braid weave & impedance of the shield will show differences. All these issues were addressed in the measurements I already posted

- Ferrite compound in the cable dielectric will matter in reducing RF noise

- for a differential receiver, such as a USB receiver, the impedances, with respect to ground, of the two signal lines is what defines an interface as balanced or unbalanced. The degree of impedance matching determines the ability of the receiver to reject common mode noise i.e noise which is on both signal lines. So, cable differences in configuration of the twisted signal wires with respect to the balance of their impedance to ground wire determines the common-mode rejection of noise. So this is one way that "a USB cable CAN reduce or eliminate noise leaking from ground loops"

Sonitus, how often have you had to use the ground lift of your DI USB Pro?

 

[Roly1650]

What Rane actually say, from the article linked earlier in the thread, (the same article being quoted as the source of measurements"). Note, the usb cable specification calls for twisted shielded pairs on the data lines. Also note no specific recommendation on the construction of the shielding, it appears the twisted lines are much more important.

"Cable Shields
Nearly all interference below a few hundred kHz is magnetically coupled. Cable shields provide almost no magnetic shielding in this range. On the other hand, twisting is very effective against magnetically coupled interference. In general, rejection of magnetic fields is proportional to the number of twists per unit length (called the “lay”) and the uniformity of the twisting. Structured cable (CAT5, etc.) achieves its relatively high noise rejection by virtue of a high twist ratio. For a century, virtually all telephone lines have run for miles on unshielded twisted pairs. In his seminars, Neil Muncy demonstrates the importance of twisting by running a very long string of mic cables around a lab and using them to connect a mic in an acoustically isolated container to a small mixer/amp that feeds loudspeakers for the audience with a lot of gain. He then takes a tape eraser (for you youngsters, that’s a big coil driven by the power line to generate a big 60 Hz magnetic field to erase magnetic tape) and moves it along the mic cable. No hum is heard with the demagnetizer anywhere along the cable except at the connectors, where it can get fairly loud. Why? The twisting is interrupted at the connectors! Twisting is also important for good RF rejection. It’s quite common for untwisted parallel cables (zip cord) to couple RF into equipment when used as loudspeaker cable, and for the interference problems to be solved when it is replaced by an unshielded twisted pair. Yet another reason to avoid most high futility loudspeaker cables! [I never cease to be amazed at how little real science the purveyors of all that pseudo-science actually understand. After one of my rep friends went through the “training” sessions held by the manufacturer of one of the better known of these product lines, he asked them for some data he could show his technically inclined clients to back up their claims. They responded that they had no such data and no gear to measure it, but they would appreciate any data he could provide!] Cable shields are effective against electric fields, and can be quite important where there is RF interference. If the cable is short as compared to the wavelength of the interference, the shield only needs to be connected at the sending end. If the cable is much longer than about 1/10 wavelength, the shield needs to be as continuous as possible and connected at both ends. As noted earlier, the ideal connection is a concentric one. Next best is the shortest practical pigtail. So, to summarize, the “right” way to terminate balanced cable, whether for audio or data, is to maintain the twisting as carefully as possible right to the point where it enters equipment (ideally there should be “zero length” of untwisted cable). If the shield is to be terminated, there should be either a concentric connection or the shortest possible pigtail, and it should go straight to the shielding enclosure of the equipment. If the connection is needed to shield against VHF RF but needs to be interrupted at lower frequencies to prevent shield current, a capacitor should be used in series with the shield connection (also with very short leads or a concentric connection), and only at the receive end."

 

[BiggerHead]

Twisting protects only for differential noise along the usb cable itself.   Snce we're not talking about problems with the digital readout I don't see much reason to care if it's differential or common mode.  If anything maybe common mode noise is worse. 
 
Anyway, It does nothing for common mode noise, or for the entire rest of the ground loop including the power cables.  I suppose you could twist your power cords too if you want the hot AC line to have balanced noise with the ground, but I don't really see that that would clearly help things at the DAC.  Noise is funny and you kind of never can be sure, but it doesn't seem that twisting offers a fundamental solution here.
 
Keep in mind that the current in a loop is determined by the sum total of magnetic flux (actually changes therein) passing through the WHOLE loop.  Of course that's a common mode current (unless you think of the loop as two wires out and back).  Yeah.. maybe we can balance it as equal (and not opposite) current on two wires, each going around the loop.  So what?

 

[mmerrill99]

Twisting protects only for differential noise along the usb cable itself.   Snce we're not talking about problems with the digital readout I don't see much reason to care if it's differential or common mode.  If anything maybe common mode noise is worse. 

Anyway, It does nothing for common mode noise, or for the entire rest of the ground loop including the power cables.  I suppose you could twist your power cords too if you want the hot AC line to have balanced noise with the ground, but I don't really see that that would clearly help things at the DAC.  Noise is funny and you kind of never can be sure, but it doesn't seem that twisting offers a fundamental solution here.

Keep in mind that the current in a loop is determined by the sum total of magnetic flux (actually changes therein) passing through the WHOLE loop.  Of course that's a common mode current (unless you think of the loop as two wires out and back).  Yeah.. maybe we can balance it as equal (and not opposite) current on two wires, each going around the loop.  So what?

Just to clarify between differential & common-mode noise for the reader. Differential noise is where the noise is on both signal wires but 180degrees out of phase with one another - in other words noise on one signal wire has the opposite noise on the other signal wire. Common-mode noise is where it appears on both signal wires equally i.e no phase differences between the signal. I think Biggerhead has it the wrong way around?

A USB receiver is a differential receiver i.e it compares the signal on D+ with D- & the voltage difference between them. If it's above a certain voltage, it's considered a "1" bit & below a certain voltages, a "0" bit.. Common-mode noise, if equal on both wires should cancel out but there are some provisos to this.

Twisting the wires in the USB cable (or any cable) is a way to ensure that any external electrical noise appears on both signal wires equally & in this way, should be cancelled by the USB differential receiver. But as I said in my previous post, it's the equal impedance of the two wires to ground that is also important for this cancellation of noise. So in a cable, the consistency of the twist of the two wires (the lay) & the orientation of the ground wire with respect to the twisted wire are of importance for optimum noise cancellation.

When shields are introduced in a cable it complicates matters & the possibilities of converting common-mode to differential-mode noise & the two USB devices now have two ground connections between the devices so it greatly increases the possibility of a ground loop (note the use of connecting the shield at only one end in the above Rane document)

 

[castleofargh]

 this is nice and all, but we're not dealing with subjective questions here. those stuff aren't a matter of opinion.
we all have several USB cables, we can all run something like RMAA, or just record music in a loop and see with audio diff maker how much of a change we achieve, or more serious stuff for those with actual measurements gears.
talking about one variable at the time is a total waste of time. of course we can alter the signal with a cable, with any cable, even more so if we start adding stuff to it and if we part from the specs agreed upon by convention.
what really matters is the fidelity of the output signal after the DAC. there, not only do we see if there is a difference, but how much it really impacts an audio signal. different chipsets will react differently to different kinks and magnitudes of signal degradations, so of course we can play the paranoid audiophile chickens and declare that whatever ludicrous speed value isn't enough or that I need a USB cable that can still do bit perfect when close to the sun, else music is crap.  but for sound science, I would expect measurements of the DAC output to be what actually matters before talking about improvements.
 
please people if you are sure that USB is an important matter where the default USB cable properties aren't the best choice for sound, present some evidence of it, at least for your very own system.
is a USB cable that can do higher speeds better for music? or like the jitterbug thing, is it somehow good to slow down the rise time with a low pass?

do we need nuclear plant shielding in our house to play music? or do I even need to twist my cables when the data is digital and the threshold for 1 is pretty high in voltage? shouldn't we just move to another place and ask a doctor if we are still OK?
whatever the question, arguing about the possibility of a problem won't give any actual answer about the usual average use for music listening. so if some of you have fancy mega audiophile cables, bring in some measurements of your DACs with different cables. or if you don't mind, send your super cable to someone with some nice measurement rig. that would help us move forward in that topic.
 
 
I tried a few of my USB cables, but I don't have amazing measurement rig(it was even worst at the time), and tried only the USB cables that came with the stuff I had bought over the years, because cables are the very last place where I want to spend money for audio quality. I might accept that some changes can occur due to cables. I might even accept that sometimes those changes can actually be positive ones.  but not that a 1000$ cable will give me the extra fidelity of adding 1000$ for a better pair of speakers or headphones.
still if some cables really improve upon the default USB standard(and I'm talking standard, not 10year old crap cable chewed up by your rabbit), I'm very interested in seeing actual evidence of it.

 

[BiggerHead]

We're not talking about speeds or bit perfectness.  Did you read any of the recent conversation?  We're talking about analog noise that comes in on the ground to the analog side.  I don't see why people just refuse to even discuss this as if usb cables exist in some virtual computer.
 
mmerril DID show measurements and, and if you count an isolator as a cable, showed improvements in measurements, although it was from a manufacturer, but it appears one that maybe doesn't cater primarily to audio for better or worse.  There HAVE been several reported cases of people hearing obvious noise and or ground hums coming in through the cables.  This has NOTHING to do with bit rate or it perfectness or anyway damaging the digital signal.  It's unrelated.
 
There is no spec for how good a DAC must be at rejecting ground noise is there? DAC output isn't governed by a protocol. Now if the only solutions to these possible problems are $300 isolators then we probably should be talking about problems that exist on pretty decent quality DAC's. (the ground lift thread was about and "audiophile" dac, sounded decent) and so that gets more quesiontable maybe.  The discussion is if cheaper fixes, ground lfiting or quality $20 cables can impact any of it, then it becomes relevant for lesser quality DACs too.
 
While I've been a bit skeptical about some of the cheaper non-isolating fixes, hence pointing out how twisted pair doesn't help,  I really don't understand the flat out objections to the conversation.  One can argue this is a rare problem. ok. I'd actually be a bit surprised if it's never a problem.    This doesn't have to be a win or lose debate does it?

 

[mmerrill99]

We're not talking about speeds or bit perfectness.  Did you read any of the recent conversation?  We're talking about analog noise that comes in on the ground to the analog side.  I don't see why people just refuse to even discuss this as if usb cables exist in some virtual computer.

mmerril DID show measurements and, and if you count an isolator as a cable, showed improvements in measurements, although it was from a manufacturer, but it appears one that maybe doesn't cater primarily to audio for better or worse.  There HAVE been several reported cases of people hearing obvious noise and or ground hums coming in through the cables.  This has NOTHING to do with bit rate or it perfectness or anyway damaging the digital signal.  It's unrelated.

There is no spec for how good a DAC must be at rejecting ground noise is there? DAC output isn't governed by a protocol. Now if the only solutions to these possible problems are $300 isolators then we probably should be talking about problems that exist on pretty decent quality DAC's. (the ground lift thread was about and "audiophile" dac, sounded decent) and so that gets more quesiontable maybe.  The discussion is if cheaper fixes, ground lfiting or quality $20 cables can impact any of it, then it becomes relevant for lesser quality DACs too.

While I've been a bit skeptical about some of the cheaper non-isolating fixes, hence pointing out how twisted pair doesn't help,  I really don't understand the flat out objections to the conversation.  One can argue this is a rare problem. ok. I'd actually be a bit surprised if it's never a problem.    This doesn't have to be a win or lose debate does it?

Well my experience of this "science" section is that there is very vocal group who have little regard for scientific knowledge (or even engineering knowledge) & a very high level of dogmatism being passed off as "science"
Just look at the comments on page 1 regarding the article quoted & what was said about the statements in that article - universal condemnation. Now compare where we have reached after 13 pages of argument - arguments mostly against the facts & measurements I posted (& I have been the only one posting measurements). Most of the statements in that article are borne out by a deeper understanding of the engineering principles of USB & USB cables. I have to say that most of the commentators on this thread have been woefully lacking in any such knowledge & their disdain for the statements in the article was borne out of ignorance, rather than any science or knowledge.

What Castle is doing here is changing the goalposts now that there seems to have been overwhelming evidence that there are many differences in USB cables that can result in measureable differences - now this has to be shown to be a measureable difference on the output of a DAC. I've seen this before & if there was a measureable difference on the DAC output the next demand/hurdle would be to show an ABX test which correlated with this difference & finally it would have to be shown in a blind preference test - after all these changes might make something worse

Castle, before you test a cable why doesn't someone explain Rueben's experience - how did his badly connected USB cable result in the sound changing to mono & distant? What's happening - bits being dropped or something else?

 

[BiggerHead]

ok... but your last statement is off track I think.  Sound changing to mono means something was broken, shorted, cross-wired etc.  That's very different than -75 db of noise.

 

[BiggerHead]

although I have to say in digitial I'm not exactly sure how that happens.

 

[mmerrill99]

although I have to say in digitial I'm not exactly sure how that happens.

Yes, that's exactly my point!!

Just a reference back to this comment from page 1

"What I also found amusing was the idea that errors in transmission would lead to changes in tonal balance, timbre, soundstaging or other sonic subtleties.

When, in reality, transmission errors happen it's obvious because you get dropouts or buzzsaw digital distortion."

 

[castleofargh]

Well my experience of this "science" section is that there is very little regard for scientific knowledge (or even engineering knowledge) & a very high level of dogmatism being passed off as "science"
Just look at the comments on page 1 regarding the article quoted & what was said about the statements in that article - universal condemnation. Now compare where we have reached after 13 pages of argument - mostly against the facts & measurements I posted (& I have been the only one posting measurements). Most of the statements in that article are borne out by a deeper understanding of the engineering principles of USB & USB cables. I have to say that most of the commentators on this thread have been woefully lacking in any such knowledge & their disdain for the statements in the article was borne out of ignorance, rather than any science or knowledge.

What Castle is doing here is changing the goalposts now that there seems to have been overwhelming evidence that there are many differences in USB cables that can result in measureable differences - now this has to be shown to be a measureable difference on the output of a DAC. I've seen this before & if there was a measureable difference on the DAC output the next demand/hurdle would be to show an ABX test which correlated with this difference & finally it would have to be shown in a blind preference test - after all these changes might make something worse

Castle, before you test a cable why doesn't someone explain Rueben's experience - how did his badly connected USB cable result in the sound changing to mono & distant? What's happening - bits being dropped or something else?

oh if it's about weird stuff that can happen, I have(had?) one usb cable that gave me more crosstalk. I have no idea as to why, but it was one cable and the measure was significantly worst than the others wich themselves measured shockingly the same(withing RMAA usual variations). so my conclusion was simply, "this cable is crap".
but again I never owned anything special for USB, no fancy audiophile cable, no magic boxes. so all I have is one crosstalk anecdote from one cable. it has no value for properly working USB systems. 
 
that's why I would love to see actual measurements of a DAC output being improved in any significant way by a cable or any other tweak, and then if possible see a bunch of other cables on the same system to make sure it wasn't 1 good vs the one crappy dysfunctional cable the guy had. and then even better, have those cables sent to some other dudes with other DACs who would also measure their DAC output with the different cables.
then we would have measurement and repeatability. sounds pretty sciency to me.
 
now if asking for measurements in sound science, on matters that are totally objective, must also be interpreted as me making plans for my ABX agenda, just make me a list of the stuff I can still say without you going paranoid. this is getting a little ridiculous.
 
 
 

  We're not talking about speeds or bit perfectness.  Did you read any of the recent conversation?  We're talking about analog noise that comes in on the ground to the analog side.  I don't see why people just refuse to even discuss this as if usb cables exist in some virtual computer.
 
mmerril DID show measurements and, and if you count an isolator as a cable, showed improvements in measurements, although it was from a manufacturer, but it appears one that maybe doesn't cater primarily to audio for better or worse.  There HAVE been several reported cases of people hearing obvious noise and or ground hums coming in through the cables.  This has NOTHING to do with bit rate or it perfectness or anyway damaging the digital signal.  It's unrelated.
 
There is no spec for how good a DAC must be at rejecting ground noise is there? DAC output isn't governed by a protocol. Now if the only solutions to these possible problems are $300 isolators then we probably should be talking about problems that exist on pretty decent quality DAC's. (the ground lift thread was about and "audiophile" dac, sounded decent) and so that gets more quesiontable maybe.  The discussion is if cheaper fixes, ground lfiting or quality $20 cables can impact any of it, then it becomes relevant for lesser quality DACs too.
 
While I've been a bit skeptical about some of the cheaper non-isolating fixes, hence pointing out how twisted pair doesn't help,  I really don't understand the flat out objections to the conversation.  One can argue this is a rare problem. ok. I'd actually be a bit surprised if it's never a problem.    This doesn't have to be a win or lose debate does it?

my stand on exotic devices having exotic problems is that those products should be burned, not that we should concern ourselves with ways to turn a donkey into a race horse.
sure problems do exist, ground loop can happen, noise reaching the analog signal can happen,(my all time favorite was when moving my mouse would be audible in my headphone. it was many years back but it sure was something mystic).  but are they specific USB problems? not really. can we find a DAC or a computer that will not have those troubles under the same circumstances? usually yes.
so what's the conclusion? that usb cables or other tweaks do matter and can improve the sound over perfectly fine random cables? that random cables are rarely up to USB specs(certainly a possibility)? or that people should stop buying the DACs or motherboards that are known to present those troubles? I know that I've made up my mind on the matter. if adding a ferrite bead or trying to deal with the ground, or getting a proper 5V can be done by adding some crap cable/magic box, it could also have been done by the DAC designer.
so I know who I'm blaming if I ever need to add that myself.
now if the actual USB cable(and only cable) can positively affect the signal fidelity of most DACs, then sure, let's discuss that. but again I'll ask for measurements of the DACs outputs with different cables. it seems obvious to me that objective improvements can only be demonstrated through measurement. I put in speed because it's my own casual questions(I never had to think about it before the jitterbug gizmo. it was meant to show that it wasn't very productive to focus on just one point in theory without looking at the global result at the output. even less so when different DAC chipsets do different operations and have different needs when it comes to signal fidelity. and no we don't need to make it a win or lose debate, but for once we're not dealing with subjective stuff, and most people can test at least a few parameters for themselves. so I hope that we can actually go somewhere with practical tests for once.
because while I've seen most of the stuff posted already, in practice I'm still inclined to believe that RMAA like those from archimago testing a few USB cables are a more realistic approach to what really matters for the casual music listener.
because specific problems will always need specific solutions. not everybody advises people to buy a usb to optical converter, yet of course it can solve some specific problems. just like not everybody needs to add another power supply of 5V, if it was so important, why are we ever paying for usb powered DACs? etc etc.  it's all a matter of drawing a line between consistant problems with their potential solutions, and anecdotal problems often coming from somebody's mistake.

 

[spruce music]

Reminds me of a recent thread on another forum.  It was asking if the hype about USB was overblown and the myriad problems of USB didn't indicate going that route was a mistake. 

The reasoning was you have these cables being so detrimental and goods one being necessary for 'good' USB.  You need these regulated 5 volt supplies.  You need this Regen, Intono or Corning optical links.  Connecting two devices via USB has become an entire cottage industry of its own.  You would get the idea USB for audio is fraught with horrid difficulty and mind really think it was just a bad idea.  Almost as if it were more fragile than LP rigs.  Which really are picky little beasts to keep in fine form, quiet and steady and optimally functioning.
 
On the other hand, no one can measure any benefits in the audio outputs with these.  Or in some cases these devices introduce some problems.  The designers of these things often have shaky theory or say they don't know it just works listen to it or admit they can't find a measured difference.  So we have neophytes fearing the USB.  Great gnashing of teeth on what best approach to take and hope USB is usable.  When in fact, asynchronous USB seems a wonderful way to largely isolate the computer from the audio system and get terrific measured and heard results. 
 
Somehow we have this burgeoning chicken little USB industry grown like mushrooms from a pile of .......shall we say anecdotal missteps.