USB cable group test in HFN

[adamdea]

I base my opinions about USB cables on the auditioning I have done, which is more than can be said of some of the posters here.

Incidentally (not that it's the point) I can't hear any difference using my dac between toslink or coax or usb (including different cables on each) or ethernet.

I am also so perceptually-challenged that I can't tell whether other posters have listened to different cables.

Obviously though I recognise that anyone who hasn't heard a £6500 cable in their own system isn't really qualified to comment. In fact anyone who hasn't paid £6,500 for a usb cable isn't really qualified to comment on whether its good value for money. If we want a proper unbiased opinion, we must ask people who have bought £6,500 cables

 

[formbypc]

Perhaps so, but that doesn't make it right, nor reduce my right to comment on how flawed the tests were as presented.

... but as reported, the tests were flawed to the point of being meaningless.

What were the flaws?

The article and contributor columns tell us the listening sessions took 'many hours', that the results from separate sessions were cross-referenced for consistency, and tell us the equipment and music used. We're also told the the listeners were kept in the dark about which cable was being used when, and also about the names and types of cables used.

Beyond this, what can you tell us about the methods they used, and what you perceive as the flaws?

 

[maxflinn]

formbypc, do you believe that different HDMI cables offer different pic/audio quality?

 

[Whaleblue]

Digital cables, like the name implies are used to pass bits from one side to the other.
Bits are 0's and 1's. There's no grey area between a 0 and a 1.

Michael

Michael,

The problem with this over-simplified argument is that electrical cables don't know what 0's and 1's are. They carry eletrical signals. 0's and 1's are represented by voltage levels. To make an abstract example 0 to 0.5 v represents a "0" and >0.5 to 1 v represents a "1". Of course the grey area is around 0.5 v in this example.

The reality that is being argued is that "0" nearly always comes out as a voltage between 0 and 0.2 v and "1" as between 0.8 and 1 v. And in the very unlikely event that 0.5 v, or thereabouts, is seen a re-request for the packet to be sent is made. Hence no slightly wrong data is ever used.

Apologies for the gross simplication I'm making here but I hope you see why "bits is bits" is an incomplete argument.

 

[Whaleblue]

[...] (like the taste of strawberries)[...]

Slightly off topic - have you ever tried pepper on strawberries? They don't taste like strawberries with pepper on them, they taste more strawberryee.

A wierd but potentially valuable fact.

 

[Whaleblue]

Other people's subjective perceptions do not call scientific fact into question.

It works the opposite way.

I think what I've been tryingto say all along Max is that there is a danger of being an absolute objectivist.

Newton's laws appeared to hold until they were disproved as being the be all and end all.

I'm still not disagreeing that you're probably right about USB cables, but to reject all subjective evidence no matter how it mounts up just because it doesn't agree with the "facts" is surely not intelligent.

 

[Ian M]

What were the flaws?

The article and contributor columns tell us the listening sessions took 'many hours', that the results from separate sessions were cross-referenced for consistency, and tell us the equipment and music used. We're also told the the listeners were kept in the dark about which cable was being used when, and also about the names and types of cables used.

Beyond this, what can you tell us about the methods they used, and what you perceive as the flaws?

The problem I had with the review was not what it told us but what was not revealed. How many people were in the group? Who were they? How many sessions? Were the same people at each session? How many times was each cable listened to? Was there a process of elimination? etc. etc.

 

[clivem2]

Here's some info on the USB cable spec followed by some info about what I've tried. Note that only the data wires are twisted and even this is optional for low speed transfer.


USB requires a shielded cable containing 4 wires.

Two of these, D+ and D-, form a twisted pair responsible for carrying a differential data signal, as well as some single-ended signal states. (For low speed the data lines may not be twisted.)

The signals on these two wires are referenced to the (third) GND wire.

The fourth wire is called VBUS, and carries a nominal 5V supply, which may be used by a device for power.

The impedance spec is rather wide 76.5 Ω minimum; 103.5 Ω maximum


I've seen people state that the power lines being adjacent to the data lines causes uneven impedance, of course the longer the cable the worse this becomes. This many be the reason for the wide impedance spec.

Here's a generic USB cable layout:



It's likely many of the audiophile cables use very individual layouts.

Here's an audiophile cable layout by Wireworld:



What started me comparing USB cables was when I tried an A to B adapter from laptop to DAC. I found the sound was different to a typical 2m generic cable. I then tried shortened cables and found these to be better
than the longer ones. My best cable which was (close in sound to the straight-thru adapter) was from a Seagate drive. I tried some audiophile cables but found they sounded different again but none
were in totality to my liking.

A to B adapter:


So far I'd found I prefered shorter cables and the adapter best of all. I then made what is a non-compliant cable missing the VBUS wire and I've no idea what the impedance is, this sounded the same as the A to B adapter:


I've tried 30cm and 50cm cables without the VBUS wires, these sound the same as the very short cable I made.


- Did I do any blind testing? No.

- Can I be sure what I find in my system is globally applicable? No.

- Am I sure enough that All USB cables don't sound the same? Yes but I can't define all the required environmental variables.

- Are differences in sound due to digital data being corrupted? I doubt it.

- Should anyone believe me? No, they should try some cheap as chips experiments for themselves.

 

[adamdea]

Michael,

The problem with this over-simplified argument is that electrical cables don't know what 0's and 1's are. They carry eletrical signals. 0's and 1's are represented by voltage levels. To make an abstract example 0 to 0.5 v represents a "0" and >0.5 to 1 v represents a "1". Of course the grey area is around 0.5 v in this example.

The reality that is being argued is that "0" nearly always comes out as a voltage between 0 and 0.2 v and "1" as between 0.8 and 1 v. And in the very unlikely event that 0.5 v, or thereabouts, is seen a re-request for the packet to be sent is made. Hence no slightly wrong data is ever used.

Apologies for the gross simplication I'm making here but I hope you see why "bits is bits" is an incomplete argument.

Actually AFAIK it's more robust than that. At least with S/PDIF (and I assume that similar principles will apply to usb). It is a transition between low and high which marks a bit, as in the fact of a change, not the judgment of where something falls on a boundary. There is a change from low to high or high to low with every bit. (it's a while since I last read up on this- it may even be low -high-low) If there is no change there is no bit .

It is pretty much impossible to miss the fact of a change from low to high- it does not matter whether it's a square wave a triangular wave, a sine wave or whatever . This is why the scopes showing "distorted" digital signals are irrelevant. It is not about making judgement calls about whether .499 should be a high or a low. Its about going from 0 to 1 or maybe 0 to 1 to 0. In this case it doesn't matter whether its going from 0.01 to .99 or .1 to .9, it has to be messed up beyond belief for the transition not to get through. If it doesn't get detected, no bit is transmitted! The robustness of this was tested with S/PDIF/AES and it could survive many many nanoseconds of jitter

Basically you need heroic levels of jitter to prevent the data being correctly transmitted and if you have it, the result is likely to be loss of lock not wrong bit.

If anyone has a better knowledge of how this works with usb I would be delighted to know

Unless you are using USB bulk mode than AFAIK there is no error correction, although there can be error detection. (I was told this about asynch usb by John Swenson on the squeezebox froum; it is certainyl true of S/PDIF). This is different from ethernet, obviously, where there is detection of errors and retransmission, and also from cd reading where there there is data redundancy and error correction.

 

[adamdea]

Slightly off topic - have you ever tried pepper on strawberries? They don't taste like strawberries with pepper on them, they taste more strawberryee.

A wierd but potentially valuable fact.

I remember having strawberries served to me with something one wouldn't have expected. I think it was pepper. It wasn't so much a weird experiment as a Heston Blumenthal style think-out-of-the-box cuisine moment.

Some people put a bit of salt in hot chocolate too.

 

[Werner]

Newton's laws appeared to hold until they were disproved as being the be all and end all.

Newton disproved. Again.

Then why is Newton still good enough for 99.9% of all engineering, including interplanetary travel?

The article and contributor columns tell us the listening sessions took 'many hours',

With 10 cables, 4 musical excerpts, and 3 listeners a rigorously-conducted test will easily last days, and be lethally boring.

The problem I had with the review was not what it told us but what was not revealed.

Indeed. To the layman a claim of blind testing may give an aura of authority. But more is needed than just keeping the cables hidden from the listeners. Much more.




It may well be that these people observed reliably and repeatably existing differences. But the way it is reported conveys no authority in this case.

 

[formbypc]

formbypc, do you believe that different HDMI cables offer different pic/audio quality?

HDMI cables? I have no opinion one way or the other.

 

[maxflinn]

I think what I've been tryingto say all along Max is that there is a danger of being an absolute objectivist.

Newton's laws appeared to hold until they were disproved as being the be all and end all.

I'm still not disagreeing that you're probably right about USB cables, but to reject all subjective evidence no matter how it mounts up just because it doesn't agree with the "facts" is surely not intelligent.

I'd say fair enough, as your position is fair, you're open minded and looking from all angles, but, in my experience from dealing with believers in HDMI cables, you can't give them an inch or they take a mile, if they think there's even a 0.00001% chance that in a given scenario, differences might be even remotely possible, they magnify it, give it legs, shout it from the rooftops and, lo and behold, differences exist

As I say, I'm aware of what I and seemingly many others believe to be concrete, scientific knowledge, that dictates the differences claimed are simply not possible, therefore I'm not prepared - in the context of this debate - to give that inch, that one tiny window of opportunity for exploitation, that may end up creating the kind of curiosity and doubt that PM has intended, in his clear attempt to boost his advertisers Foo sales.

 

[pure sound]

Presumably you've also sent PM that email. Any reply yet?

 

[formbypc]

I'm not prepared - in the context of this debate - to give that inch, that one tiny window of opportunity for exploitation, that may end up creating the kind of curiosity and doubt that PM has intended, in his clear attempt to boost his advertisers Foo sales.

How many of the ten manufacturers actively advertise in HFN, though...?

 

[Whaleblue]

Newton disproved. Again.
Then why is Newton still good enough for 99.9% of all engineering, including interplanetary travel?

Werner, I'm surprised at you I chose my words carefully "disproved as being the be all and end all"

Although Newtron's laws are 99.999% correct they have been found offer a slightly incomplete picture. That was the point I was trying to make.

 

[Whaleblue]

[...]therefore I'm not prepared - in the context of this debate - to give that inch, that one tiny window of opportunity for exploitation, that may end up creating the kind of curiosity and doubt that PM has intended[...]

I understand where you are coming from, but to not give the inch puts you at a disadvantage when it comes to being taken seriously.

The words I have emboldened are the underpinnings of much (most?) scientific research.

I appreciate the significat caveat you give them here nonetheless.

 

[TPA]

I don't use these usb things but it would save a lot of grief if a handful of peeps just got together and carried out a definitive test on the matter. It can't be that hard.

 

[Mescalito]

Why not just use an ethernet based solution? Or has some golden-eared dingbat heard differences between different brands of Cat 5 cable?

Chris

 

[Werner]

Newtron's laws are 99.999% correct they have been found offer a slightly incomplete picture. That was the point I was trying to make.

And thus implying that there are Einstein laws for audio just around the corner, waiting to be discovered? Newton breaks down in extreme circumstances, either very small thingies or very fast thingies, which have no consequence in daily physics. Is audio operating at the edge of some such extremity that might warrant an entirely new view on things?

Why not just use an ethernet based solution? Or has some golden-eared dingbat heard differences between different brands of Cat 5 cable?

Don't worry, situation is perfectly normal.

http://www.audioquest.com/ethernet/diamond