Double Blind Testing Prices All Power Cords Have An Effect On Audio!!!!!

[kumakuma]

10 minutes ago, marce said:

The whole point of the USB specification is that in the case of cables, transmission lines etc. they are kept at 90R differential impedance, that is the important figure and in that respect they should all measure the same if true USB.

 

I'm sorry but I'm only going to believe you if you provide me with a full description of your home audio system, a notarized copy of a recent hearing test by a licensed audiologist, and references from three other audiophiles.

[mansr]

16 minutes ago, marce said:

The whole point of the USB specification is that in the case of cables, transmission lines etc. they are kept at 90R differential impedance, that is the important figure and in that respect they should all measure the same if true USB.

The spec allows for a 15% deviation, and cables might also vary in DC resistance. The important thing is that with a conforming source and cable, the eye pattern at the receiver will be within the defined limits, thus allowing correct recovery of the transmitted data. It is perhaps conceivable that a (poorly designed) DAC might be affected by noise carried, one way or another, over the USB cable and that differences in shielding or whatever between cable models might influence this. Even then, however, the descriptions of the effects (radically altered frequency response, etc) are entirely unreasonable. This suggests, to me, that the reported experiences are more likely imagined than the result of any real electrical differences.

[Paul R]

46 minutes ago, kumakuma said:

 

I think "measure the same" is a meaningless expression. I would be surprised if there were two different USB cables that are absolutely identical in terms of all measurable electrical parameters.

 

Totally agree. Still don't understand how the cable can make any difference at all in a USB connection, not really. Best guess is leaked electrical noise, but that is incredibly hard to prove, even with a USB analyzer. At least, with any USB analyzer available to me.  

-Paul 

 

[Paul R]

44 minutes ago, Allan F said:

 

Actually, Gordon Rankin of Wavelength Audio did some measurements of USB cables about five years ago and found deviations from the 90 ohm impedance specification. He offered an explanation of why this affected the sound. That even caused George to post this mea culpa as a consequence. Gordon Rankin Says I'm Wrong About USB Cable Sound!

 

I thought that was George saying mea culpa? When Gordon told him -yeah - these USB cables do sound different.  

 

In any case, sound different they do, despite transmitting data perfectly with no errors. Now USB is a totally different category from Ethernet, which I have a very difficult time accepting can make a difference in audio quality. 

 

Everyone has a point where their suspension of disbelief crumbles - some are just further into the wilds than others. 

 

-Paul 

 

[Paul R]

16 minutes ago, mansr said:

The spec allows for a 15% deviation, and cables might also vary in DC resistance. The important thing is that with a conforming source and cable, the eye pattern at the receiver will be within the defined limits, thus allowing correct recovery of the transmitted data. It is perhaps conceivable that a (poorly designed) DAC might be affected by noise carried, one way or another, over the USB cable and that differences in shielding or whatever between cable models might influence this. Even then, however, the descriptions of the effects (radically altered frequency response, etc) are entirely unreasonable. This suggests, to me, that the reported experiences are more likely imagined than the result of any real electrical differences.

 

Have you listened to different USB cables on the same DAC?  Or on a couple different DACs?  The differences, in absolute terms are of course, small. In relative terms, against each other, they can be pretty large. 

 

A USB cable isn't going to make a system unlistenable, and there are DAC / Computer combinations that are pretty well immune to changes in USB cables. But the silly things do make a difference, as unreasonable as it seems. The experiences are not imaginary, at least not all imaginary. Nor, amazingly enough, does the price of the USB cable seem to matter. A $10 Belkin cable seems to be really good, while a $250 Nordost can sound lousy. Go figger... 

[Allan F]

25 minutes ago, Paul R said:

I thought that was George saying mea culpa? When Gordon told him -yeah - these USB cables do sound different.

 

Sorry, Paul, somehow we have our wires crossed. Yes, it was George's post and he did say "Mea Culpa, I guess", acknowledging that he was at fault.

[mansr]

1 hour ago, Allan F said:

Actually, Gordon Rankin of Wavelength Audio did some measurements of USB cables about five years ago and found deviations from the 90 ohm impedance specification. He offered an explanation of why this affected the sound. That even caused George to post this mea culpa as a consequence. Gordon Rankin Says I'm Wrong About USB Cable Sound!

Seems like even George was hoodwinked.

 

On 6/16/2014 at 10:18 PM, gmgraves said:

Mea Culpa, I guess. I just had a nice discussion with Gordon Rankin of Wavelength. Gordon is the man who designed the Ayre QB-9 and the AudioQuest DragonFly DAC, as well as the WaveStream® IsoSynchronous USB protocol. He said a number of things that really took me aback. The first thing he said was that yes, USB cables do sound different. They shouldn't but they do. He says the reason is because most manufacturers are unable or unwilling to make their cables with the correct 90 Ohm impedance and be able to pass up to a 2.6 GHz perfect square wave. He says that unless those two parameters are met, the USB feedback mechanism doesn't work because reflections get the signal confused on the computer end. Without it, there's no way for the computer to know that it's sending the data at the proper rate and bits get dropped. Since USB receivers have no error correction (this was news to me) a dropped bit gets interpolated at the DAC, and distortion increases. He says that this situation is not helped by the fact that Windows, including Win 8, generate 12% more hard errors in a digital audio bitstream than does Apple's OSX! He also says to play your computer audio directly from memory for lowest error rate on either platform, and if possible, keep your music on a Firewire, eSATA or Thunderbolt drive rather than USB.

Pretty much all of that is utter nonsense.

[Ralf11]

11 hours ago, sandyk said:

Paul

 I may not be winning this argument anywhere near every time, but I sure as hell have a great deal more of member support than I did originally 10 years ago

You can see many members now think ( and experiment ) for themselves, instead of blindly accepting everything the "Experts" insist is correct.  This is way more obvious in areas other than the General Forum area. 

Even Ralf11 has conceded that I have made quite a few worthwhile contributions in the important Power Supply area, as well as the Analogue area.

Alex

 

I have "conceded" nothing.  I have several times pointed out your contributions in analog circuits.  you need to learn digital.

[BrokeLinuxPhile]

USB cables are just weird.  Data and power moving next to each other just does strange stuff. 

 

I still hold the belief (although things have changed over the years) that USB is good for mice, keyboards, printers, and pen drives.  That's it.  It has bandwidth, but to get USB right you need to spend significant R&D $$$$ to get good, clean, noise free results with minimum jitter.  On both ends of the connection. 

 

Then the cable has to be just right.  Slight impedance mismatches at each end (where interconnect makes contact with device) can cause signal reflections if conditions are right in addition to circuit impedance mismatch.  If that reflected signal harmonic is just the right frequency, here comes phase alignment/cancellation issues on the data line.  Lower frequencies will have more than enough energy to reflect back to the source, all working in a big domino effect. 

[Ralf11]

1 hour ago, mansr said:

The spec allows for a 15% deviation, and cables might also vary in DC resistance. The important thing is that with a conforming source and cable, the eye pattern at the receiver will be within the defined limits, thus allowing correct recovery of the transmitted data. It is perhaps conceivable that a (poorly designed) DAC might be affected by noise carried, one way or another, over the USB cable and that differences in shielding or whatever between cable models might influence this. Even then, however, the descriptions of the effects (radically altered frequency response, etc) are entirely unreasonable. This suggests, to me, that the reported experiences are more likely imagined than the result of any real electrical differences.

 

Quoted for emphasis. 

 

I will additionally opine that different cables might lead to detectable differences with a poor DAC due to that noise.  And I'd bet on symphonic music as most susceptible.

 

We will never know w/o a listening test.

[Richard Dale]

10 minutes ago, mansr said:

Seems like even George was hoodwinked.

 

Pretty much all of that is utter nonsense.

Not sure about that. But I can make a factual correction to something George said - Gordon Rankin didn't design the Ayre QB9, it used his USB firmware but the rest of the design was done in house at Ayre as far as I know.

[gmgraves]

 

Quote

 

If you can hear a difference, that difference can be easily measured by a skilled person using the correct modern test equipment.

Unless, of course, that “difference” is being imagined by the listener as in confirmation or expectational bias. in which case it cannot be measured for the simple reason that said differences do not really exist.

[Allan F]

26 minutes ago, mansr said:

Seems like even George was hoodwinked.

 

Pretty much all of that is utter nonsense.

 

Unless one holds Gordon Rankin in higher esteem than you and believes what he has to say. Of course, that does not necessarily negate the possibility that he could be wrong.

[Ralf11]

6 minutes ago, Allan F said:

 

Unless one holds Gordon Rankin in higher esteem than you and believes what he has to say.

 

this is why scientists do experiments

 

if you work solely on the basis of "esteem" you will find many many members holding carnival barkers in higher esteem than an expert and believing in what they say

[mansr]

9 minutes ago, Allan F said:

Unless one holds Gordon Rankin in higher esteem than you and believes what he has to say.

It's a simple matter of reading the USB spec.

[Richard Dale]

2 minutes ago, Ralf11 said:

 

this is why scientists do experiments

 

if you work solely on the basis of "esteem" you will find many many members holding carnival barkers in higher esteem than an expert and believing in what they say

If Gordon Rankin has implemented USB firmware, used it in his own DACs and licensed it to other companies how can he be a 'carnival barker' who is not a USB expert?

[mansr]

1 minute ago, Richard Dale said:

If Gordon Rankin has implemented USB firmware, used it in his own DACs and licensed it to other companies how can he be a 'carnival barker' who is not a USB expert?

Knowing the truth and telling lies are not mutually exclusive.

[Ralf11]

to be clear, i'm not calling him a  'carnival barker'

 

read my post again if you think I did

[Richard Dale]

2 minutes ago, Ralf11 said:

to be clear, i'm not calling him a  'carnival barker'

 

read my post again if you think I did

Your comment was in reply to a single sentence from Allan F mentioning Gordon Rankin, I not sure what I need to read again.

[mansr]

8 minutes ago, Ralf11 said:

to be clear, i'm not calling him a  'carnival barker'

Why not?

[Paul R]

1 hour ago, gmgraves said:

 

Unless, of course, that “difference” is being imagined by the listener as in confirmation or expectational bias. in which case it cannot be measured for the simple reason that said differences do not really exist.

 

Like IMD for example? Everyone heard it but it did not exist? Until of course, it did?

 

There are hundreds of listening tests reported even just in CA George. USB cable differences are about as real as anything can be.  

 

Unfortunately, there are also reports about power cables, and differences in formats, and even differences caused by different RAM in servers. Some of these reports are without a doubt, the result of wishful listening. 

 

But certainly not all of them. Engineering minds tend to want to dismiss the lot, but that would be a mistake. 

[Paul R]

1 hour ago, mansr said:

It's a simple matter of reading the USB spec.

 

Nope. I would suggest that you look up Gordon first before making statements like this. 

 

No insult, but Gordon basically fixed USB for audio, makes some if the best DACs and amps in the world, and has probably forgotten more about USB audio than you and I combined will ever learn. 

 

It is not just a matter of reading the USB audio spec. I will apologize when you build a DAC half as good as a Wavelength DAC and write your own USB software to make it work.  

[mansr]

Just now, Paul R said:

Nope. I would suggest that you look up Gordon first before making statements like this.

I know who he is. Not that it matters. He could be Jesus Christ, and the bit I quoted would still be nonsense.

 

1 minute ago, Paul R said:

Gordon basically fixed USB for audio

Really now? I thought it was a collective effort primarily by all the people, none of which are Gordon, listed as contributors in the USB and USB Audio Class specs.

 

4 minutes ago, Paul R said:

It is not just a matter of reading the USB audio spec.

Sure is. The statements George attributed to Gordon are nonsensical in the context of the USB spec. It is of course possible that George misunderstood something.

[Ralf11]

51 minutes ago, mansr said:

Why not?

 

it was a general comment

 

R. Dale - try a simple textbook first

[gmgraves]

7 minutes ago, Paul R said:

 

Like IMD for example? Everyone heard it but it did not exist? Until of course, it did?

 

There are hundreds of listening tests reported even just in CA George. USB cable differences are about as real as anything can be.  

 

Unfortunately, there are also reports about power cables, and differences in formats, and even differences caused by different RAM in servers. Some of these reports are without a doubt, the result of wishful listening. 

 

But certainly not all of them. Engineering minds tend to want to dismiss the lot, but that would be a mistake. 

I don’t dismiss the lot. For instance, speaker cables can really make a difference, but there is a real reason for that. Amplifiers and speakers interact far more than say the output of a DAC and the input of an amp or preamp, which just need to be connected together by a reasonable length of coax. Although RG-59 has the closest impedance match, in the half-meter to 2 meter lengths commonly used in a domestic audio set-up, it’s not all that critical. 

But speaker cable (depending on the run length) can be critical to proper speaker performance. Some speakers are very cable sensitive and others (like Magnepans) don’t give a damn. 14 Ga zip cord is as good as a $10,000 run of MIT as far as they are concerned, but mY Martin Logan’s are somewhat cable sensitive. This is because the wire run becomes part of the impedance profile of the speaker an Hereford is part of the load the amp sees.

on the other hand, interconnect sound and especially mains cable sound is just nonsense with absolutely no since behind it.