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Best USB cable to use between computer and dac?


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Your posts on this topic appear to be referring to an "ideal world" system, rather than a "real world" system. I "know" that different USB cables do sound different in my system, using an asynchronous USB DAC.

OK, so "noise" running on a digital cable will not affect the accuracy of the bits-I agree up to this point, but, what does that noise affect? Well, any noise that comes to the USB receiver will get to the power supplies of the clocks through the ground plane-even if the +5VDC is not connected. Clocks are analog devices, and are very sensitive to power supply noise-so we see that it is possible for this noise to affect the quality of the digtal signal output (I2S) by affecting the clock.

Secondly: you suggest that noise on USB cables shoulde no different than noise in an analog cable, while that is one way to look at things, it is not really accurate in the real world of our system when considering USB cables. Analog cables (in a high end system context) connect together components which are designed to be as low noise as possible. But computer audiophiles use a USB cable to connect an inherently noisy environment (the computer) to the rest of our systems. Considering that the computer environment is inherently very noisy, it makes sense that USB cables should pay particular attention to reducing the impact of computer generated noise products on the DAC.

 

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Julf - I am not sure if you acknowledge hearing differences among various digital cables or just acknowledge the possibility that some differences may exist (though you have never heard any differences among different digital cables).

 

As some have stated, "YMMV". But for the benefit of others that may be interested in further reading about sonic differences in digital cables:

 

http://www.bluejeanscable.com/articles/digitalanalog.htm

 

http://www.hifi-advice.com/digital-cables-info.html

 

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If I had done it the other way, by opening the box, attaching the battery there, and disconnecting the USB power connection from the pc board, the cable would not have been involved in any way whatoever. "How I prefer to think of it" is just not the case.

 

It is, in this instance, a USB to SP/DIF converter power issue. That and only that. That it was marginally simpler to do by cutting the cable close to the converter is irrelevant.

 

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What Julf said about noise having a different effect is fact. Any noise in an analog signal simply becomes part of the signal. The noise in a USB, or other 'digital' does NOT become part of the signal. It stays as noise. It may make the bits jiggle up and down or side to side, it may get into the circuitry of the DAC, but it does not 'become' the bits, which ARE the signal.

 

Different cables certainly change the sound of an 'analog' signal, more by attentuation of various frequencies than noise, I suspect (remember, noise becomes the signal). The effect of noise in a 'digital' signal is different and not related to our 'analog' conceptions at all.

 

Different USB cables make a totally different difference than analog cables, if they make a difference at all.

 

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What Julf said about noise having a different effect is fact.

 

So? If you are saying beacuse of this there is no possible way USB cables can sound different, then that is only your opinion, and you should label it as such.

 

It is a controversial opinion, because I and other people can hear a difference in cables. That is a fact too.

 

That the difference might be caused by power or electrical noise is again opinion. That is also a controversial opinion.

 

It migHt be that you are trying too hard to get to the bottom of all these subjects, and are drawing indefensible conclusions from incomplete and inaccurate data. It's a normal problem with bright people.

 

Paul

 

 

 

 

Anyone who considers protocol unimportant has never dealt with a cat DAC.

Robert A. Heinlein

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Again you misread what I have written. I did NOT say there was no difference. I said that while there are certainly differences in the sound of 'analog' cables I have grave doubts about whether there are in USB cables. That is rather different than saying there are not and cannot be because etc etc etc.

 

BTW. Went to the toy airplane shop to buy an engine. Costs about the same as a Mac. There is an Apple Store nearby. "If they don't have the engine in stock I might take a look in the Apple Store".

 

Fortunately they had the engine I wanted :)

 

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"Do you know why? Was it because audio (or DACs) just didn't come into the issue at all when the USB spec was agreed?"

 

The oft repeated explanation is that USB was originally designed for connecting mice and printers to computers. Only later was it co-opted to support audio.

 

Note, Firewire spec allows for bus power, but also specifies isolation, which USB does not unless I've misunderstood what others have reported here.

 

 

clay

 

 

 

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"You have any facts to back that up?"

 

Of course. Otherwise I would have labeled it as an opinion.

 

Any basic textbook in signal transmission theory would do.

 

"Surveys, comprehensive and statistically significant testing?"

 

Do you need surveys or statistical testing to prove 2 + 2 = 4? Or would it perhaps be better to start with Peanon's axiom?

 

 

 

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"Your posts on this topic appear to be referring to an "ideal world" system, rather than a "real world" system."

 

No, I am talking about practical, physical systems.

 

"OK, so "noise" running on a digital cable will not affect the accuracy of the bits-I agree up to this point"

 

Excellent!

 

"anynoise that comes to the USB receiver will get to the power supplies of the clocks through the ground plane"

 

Only to the same degree as through any other connection connecting the earth/ground planes - so just like analog interconnects and power cords.

 

"Clocks are analog devices, and are very sensitive to power supply noise-so we see that it is possible for this noise to affect the quality of the digtal signal output (I2S) by affecting the clock."

 

And that effect is easy to measure. So how about presenting us with some measurements of how much the clock gets affected, and how audible it is?

 

"computer audiophiles use a USB cable to connect an inherently noisy environment (the computer) to the rest of our systems."

 

Connecting a noisy environment to an environment designed to be relatively immune to noise.

 

 

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"USB was originally designed for connecting mice and printers to computers. Only later was it co-opted to support audio."

 

Indeed. Just like computers were originally designed to solve scientific problems, and only later got co-opted to support audio. And like how vacuum tubes were originally designed for radio and telephony, and only later got co-opted to support audio.

 

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"By the way, I can think of at least twi situations where 2 + 2 does not equal 4.0. that's the oldest teaser in the book."

 

I guess you picked the wrong book :)

 

If we are talking about real numbers, then there are of course lots of situations where 2.0 + 2.0 doesn't equal *precisely* 4.0. But I did not write 2.0 + 2.0 = 4.0. I wrote 2 + 2 = 4. Those numbers are natural numbers (and integers). And thus my reference to the Peano axioms (apologize for remembering Peano's name incorrectly - it's been more than 30 years since my Number Theory 101).

 

It is very much like how some people here argue (until their face turns blue) that things that make sense in an analog word somehow directly apply to digital systems, without understanding the difference. As in "if all you know is analog, then everything looks analog".

 

Of course even a digital transmission system is analog at the level of the transmission media (the cable), but as there is a re-quantization step, the data that comes out is the same data as went in, as long as the transmission system works as designed.

 

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That is add two piles of sand and another two piles of sand to equal one pile of sand.

 

Like sands through the hourglass, so are the Days of Our Lives.

 

Now that we have wasted or spent more time (depending on your perspective), anyone care to summarize their findings for the best USB cable (or cable particulars) to use between computer and DAC?

 

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