[Willakan]

/begins chanting
Test It! Test It!
(pulls out war drum)

 

[BlackbeardBen]

Well, a properly conducted one anyway! (Removes personal biases, that is.)
 
vandaven, excellent tests.  I'm surprised they nulled that close -- -110 dB is impressive.  That's below the noise floor of 16 bit audio (obviously you were testing with 24 bit audio).  Given the quantization error of jitter, however, you'll of course never get them to null perfectly - and the uDAC 2 doesn't have the best jitter performance anyway (but not enough to make a difference to our ears, just to the measurements).
 
I've seen RMAA measurements for the noise of the uDAC 2 at 24 bit audio in the range of -96 dB -- I think that closer nulling than that should indicate that the noise is signal dependent - jitter, probably.  Still, -96 dB is in no way audible under normal listening conditions; nor is a -110 dB null.  Bob's goal (he achieved it) in the infamous Carver Challenge, for example, was a -70 dB null.  -110 dB is 1000 times less difference!

 

[vandaven]

Just for treats, I have done some further comparison to show how insignificant the difference between the cable difference is. 
 
You've all seen the spectral analysis above. That's the difference between Red and Grey. 
 
Now, I've decided to add a little bit of EQ to a pink noise signal (as the one displayed above) and compare it with the original signal, again via inverse summation. As you can see, the EQ is set to peak filtering @ 4 kHz, 0.1 dB gain. There is a high probability that this little change would not be heard by most people in A-B blind tests. 
 
Taking a look at the resulting audio file, it clearly shows an identifiable difference to the spectrograms above. 
 
In other words: That's what a hardly audible difference looks like. 
 

 

[vandaven]

Quote:

Well, a properly conducted one anyway! (Removes personal biases, that is.)
 
vandaven, excellent tests.  I'm surprised they nulled that close -- -110 dB is impressive.  That's below the noise floor of 16 bit audio (obviously you were testing with 24 bit audio).  Given the quantization error of jitter, however, you'll of course never get them to null perfectly - and the uDAC 2 doesn't have the best jitter performance anyway (but not enough to make a difference to our ears, just to the measurements).
 
I've seen RMAA measurements for the noise of the uDAC 2 at 24 bit audio in the range of -96 dB -- I think that closer nulling than that should indicate that the noise is signal dependent - jitter, probably.  Still, -96 dB is in no way audible under normal listening conditions; nor is a -110 dB null.  Bob's goal (he achieved it) in the infamous Carver Challenge, for example, was a -70 dB null.  -110 dB is 1000 times less difference!

What you see in the measurement is the SPDIF signal provided by the uDAC2, not the analog one. The audio data is delivered via USB stream to the NuForce uDAC2, clocked, and then delivered to the Mbox2 audio interface via SPDIF digital (clocked by the uDAC2). 
 
IF the USB cable would make any difference in the signal chain, it would show up, and that more clearly than thru any ADC-analog chain, where the performance of analog components, approximation and quantization.
 
Addition / Edit:
 
In regards to inverse summation and noise floor: given the noise floor is the same on recording A and recording B, it would null out too. The difference we see through nulling is basically the ONLY change at moment A and B, in this case, jitter through unstable / dirty clocking is the culprit, as the result was the same with both cables, so the only variable left in this formula seems to be the uDAC2 (which, again, should not be discussed here). I conducted a similar experiment last weekend on the original USB-cable thread in the cable part of this forum http://www.head-fi.org/forum/thread/554008/don-t-get-why-audiophile-usb-cable-would-improve-sound-quality/165 . 
In regards to the signal chain, it was a bit different, but yielded the same results. I went Mac Pro > USB cable > Mbox2 > loopback via SPDIF out to SPDIF in and back into the Mac and Pro Tools HD. Result was a complete null, no matter which cable was used. People did not believe, so I went DAC -> ADC. Again, no noticeable difference between Red and Grey, but some artifacts due to the digital-analog-analog-digital conversion which were also explained by me. 
 
Cheers. 
 

 

[BlackbeardBen]

Quote:

What you see in the measurement is the SPDIF signal provided by the uDAC2, not the analog one. The audio data is delivered via USB stream to the NuForce uDAC2, clocked, and then delivered to the Mbox2 audio interface via SPDIF digital (clocked by the uDAC2). 
 
IF the USB cable would make any difference in the signal chain, it would show up, and that more clearly than thru any ADC-analog chain, where the performance of analog components, approximation and quantization.
 
Cheers. 
 

Ahh, okay, that makes more sense!  I missed where you said that - see it now.
 
Yeah, it wouldn't make a whole lot of sense to introduce all the quantization error and analog performance issues by actually running through the DAC - the S/PDIF output is as close to perfect as we'll have short of reading the direct bit stream.
 
We'll still have the the jitter in the clocks then - but that shouldn't make a difference (when it's staying in the digital domain) unless there's enough clock drift to cause bit slip, or does it?

 

[vandaven]

Quote:

Ahh, okay, that makes more sense!  I missed where you said that - see it now.
 
Yeah, it wouldn't make a whole lot of sense to introduce all the quantization error and analog performance issues by actually running through the DAC - the S/PDIF output is as close to perfect as we'll have short of reading the direct bit stream.
 
We'll still have the the jitter in the clocks then - but that shouldn't make a difference (when it's staying in the digital domain) unless there's enough clock drift to cause bit slip, or does it?

In regards to the test, the jitter of the uDAC2 makes no difference. In regards to listening, I assume it also doesn't make a big difference.
 
If I would have to rely on the uDAC2 circuitry to submit a master digitally to a recorder, I would be quite worried, because what the digital transportation is not as clean as I wished it to be.
 
Many people believe that if a device operates at a sample rate of, let's say, 44,1 kHz, it's always 44100 samples per second. But that is far from true. The clock deviates, so at time point A, a second could be 44000 samples, and later at time point B it could be 44250 per second. What I've learned in years of audio engineering is that a stable clocking source is more important than the type of AD / DA chip a device uses. Reclocking via SPDIF is generally not the best anyway. In a professional recording studio, a studio word clock device (like an Apogee Big Ben or Rosendahl Nanosync) is used to clock all of the digital devices in the studio that are interconnected to each other. 
 
As an addition, I might want to add that some of the audio engineer colleagues of mine use USB audio interfaces for work (even though it has to be mentioned that many smaller outboard devices use a firewire connection), and none of them uses fancy aftermarket USB cables. When I told one of my dearest colleagues about this discussion here on head-fi.org, and he was quite amused why people think that any expensive USB cable possibly could add something to the sound that was recorded via a standard one (and he does some serious high-end work in the classical recording world). Analog cables are a different beast nonetheless: I remember talking to one of the top audio engineers in the world back when I was engineering a production at a very prominent recording studio here in Europe, and he told me that recabling his speaker setup with some more expensive esoteric brand (can't remember the name though) that someone else recommended him to try out enhanced the sound of his setup. 
 
 
 
 
 
 

 

[SmilingPolitely]

I only recently started browsing the Head-Fi forums with any sustained interest; it was time for me to upgrade my IEMs. It came as something of a shock to me that something so inane like the cable debate is being so heatedly discussed here, so much so that part of the discussion (DBT testing) is a bannable offence in one of the sub-forums.
 
I've always been something of a PC geek. I've been building PCs as a hobby for about 15 years now. In the course of those 15 years, I've seen many heated debates on what comprises the "best" components for a given application. But these debates are almost always based on quantifiable numbers. If a given set up runs a given game at ~125 FPS, then it runs the game at ~125 FPS. If you went over to the HardOCP forums and stated that your equivalent spec'd (also running the same game at ~125 FPS) but far more expensive system simply felt smoother, you'd be laughed off the face of the Internet.
 
I mean, even if you said you could tell the difference between a game running at 120 FPS and 125 FPS, you'd be met with more than a healthy dose of scepticism. But to claim that something perceivable at the same time simply cannot be measured? Seriously? I am in sheer awe at what takes place in these forums.
 
If it can be perceived, it can be measured. If two things are measured equal but perceived differently, then the perception is in error. Or, as was demonstrated earlier in the thread by that excellent BBC video, the perception is being deceived.
 
Thus, I have a suggestion. Instead of asking the question, "what is the perceivable difference between 2 given cables?" perhaps the question ought to be: "what is the measurable difference between 2 given cables."
 
Or perhaps that's what you've been trying to do all along. I haven't been here long enough to know otherwise. But perhaps I shouldn't stay to get stuck in the mire...

 

[jackmccabe]

^ when money is involved people become stupid.
People can also not believe there aren't differences because marketing tells them there is so they hear them and refuse to question them.

 

[DemonicLemming]

If it's banal (like a power cable or USB cord) and costs lots and lots of money, it must be good because it's expensive, yes?
 
Psychosomatic/placebo effect is always an interesting thing, especially when it coincides with a field as subjectively opinionated as audio.
 
Quote:

^ when money is involved people become stupid.
People can also not believe there aren't differences because marketing tells them there is so they hear them and refuse to question them.

 

 

[vandaven]

Quote:

If it's banal (like a power cable or USB cord) and costs lots and lots of money, it must be good because it's expensive, yes?
 
Psychosomatic/placebo effect is always an interesting thing, especially when it coincides with a field as subjectively opinionated as audio.
 


 

The problem is that in the analog realm, there are differences between cables. There is always a top or bottom line, and that clearly depends on the application (required length, required operating temperature etc.). A poorly manufactured cable will cost less than a well manufactured one, that's for sure. And people are used to that. 
 
So that is why I'd like to assume that clever manufacturers / marketing guys thought that it might as well be easy to sell pricey USB cables (that don't improve performance) or expensive loudspeaker cables to the people. And I wouldn't even go as far as saying that the conductivity / manufacturing quality / gold plated whatever is not there, it just gives no advantage over a "normal" cable at the end of the day because with USB transfer, this high precision is not required. 
 
For some people, these things are status symbols. Alright, I have no problem with that. But they don't make a difference in sound. Let's be honest, does anyone really think that an expensive Rolex knows the time better than a well manufactured "mid-priced" watch?

 

[Shike]

Quote:

The problem is that in the analog realm, there are differences between cables. There is always a top or bottom line, and that clearly depends on the application (required length, required operating temperature etc.). A poorly manufactured cable will cost less than a well manufactured one, that's for sure. And people are used to that.

The assumption that this difference costs more than a few dollars at most is ridiculous though.  Monoprice is proof that you can get reliable solid made cables cheap as all get out.  On the off chance you get a bad one (I never have compared to some other more pricey brands) they're more than willing to replace it usually.  The only time I'd pay more for a cable is if you really want something like locking RCA connectors.
 

 

[Hennyo]

Quote:

It sounds good so far - but you need to make sure you level-match all your testing.  Also, for headphone cables, you need to control the potential for feeling the difference between them in weight or feel as they brush against your head.
 
And you shouldn't get zero guesses right (out of a reasonably large sample)!  You would be expected to average about 50%, but the probability of a particular distribution depends on the number of samples.  That's why you have to do a significant number of samples.
 
I'd say more, but this really outlines what you need to know and do to properly set up an ABX test (although yours won't be double blind out of practicality):
http://www.hydrogenaudio.org/forums/index.php?showtopic=16295
 
Also, at this point wouldn't it be prudent to move this to the Sound Science forum since that's what's being talked about.
 

 
I've thought about all of these things, and I will be demoing enough signal cable to make it clear than my chance of guessing which cable it is should be about 1/8 or 1/10.
I think if I can name 8/10 correct we can assume that I am right, and the 2/10 i missed will be due to such a wide variety of cables I'll have to choose from. (Call it human error). But if I get say 1 or 2 correct, then we're withing the boundaries of probability, and sadly, we can agree cable makes no difference.
 
At this point I'm just looking for enough "aye aye!" to motivate me to do it. It's safe to say, the more people sign on, the more work I will put into it and the more professional it will be.
 
 

 

[Hennyo]

Frankly, I'm on your guy-ses side. There's no way for you to know I'm not rigging this, and for you to suggest I am really pisses me off.... I've offered to go out of my way, assemble by-standers and  their video equipment, and critically listen and report a scientific method on camera. Anybody who does believe my intentions are clear, please leave now.
 
There will be no bs involved, (again, pisses me off) I give you my word. You've gotta remember, I'm interested in this too,

so please do not insult my intentions.

 

[Hennyo]

The good news is, the test could be as soon as Tuesday, Wednesday of next week as that is when I and others might be available. (Store hours, people involved, etc.)
 
The only thing I ask is that you suspend your belief/disbelief as this is essential to science. I am willing to put my bit in, and I will post my video regardless of the results. I have given you my word there's no funny business or micheif afoot (for the cynics). I can do nothing more, I'll keep you posted.

 

[The Pell]

I dont think anyone is questioning your intentions. But, its important to keep the test scientifically valid, and I think everyone is trying to put together the most bulletproof scenario possible.