Audiophile grade USB cables

Vincent Kars

WBF Technical Expert: Computer Audio
Jul 1, 2010
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As file based audio is gaining momentum and many believe asynchronous USB the way to go there is a growing market for audiophile grade USB cables.

The question of course is why a cable can have any impact on sound quality.
Some say that improved jitter performance of a cable can make a difference.
Others say that the reason we use asynchronous USB is exactly to have zero input jitter at the DAC so all what is happening upstream is irrelevant cable included.

Audiophile USB cables are becoming as controversial as high-end power cords.

Much debate on the audio forums, measurements are rare.
Marlene’s Musings is one of the very few resources I know measuring USB cable performance.


Noise, standard cable, from SoundBlaster to ASUS: very low noisefloor



Noise, Audioquest Forest USB cable, from SoundBlaster to ASUS: much higher again on lower frequencies.

Obvious there is a measurable difference although not in favor of the audiophile cable!

Source: Marlene's Musings
 
Last edited:

FrantzM

Member Sponsor & WBF Founding Member
Apr 20, 2010
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<snip>
Marlene’s Musings is one of the very few resources I know measuring USB cable performance.


Noise, standard cable, from SoundBlaster to ASUS: very low noisefloor



Noise, Audioquest Forest USB cable, from SoundBlaster to ASUS: much higher again on lower frequencies.

Obvious there is a measurable difference although not in favor of the audiophile cable!

Source: Marlene's Musings

Of course we, audiophiles, will find a way to reject those measurements because they don't matter, we have to trust our eyes ... Sorry! Freudian slip... We must trust in this order:
  1. The Audiophile-approved brand: AudioQuest
  2. The High Price a guarantee that there was some development behind the cables
  3. And our ears
:eek:
 

DonH50

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Jun 22, 2010
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IME, which may match nobody else's, the biggest contributor from a cable to jitter is bandwidth, followed by proper impedance matching. All else is pretty much in the dust. Low bandwidth can significantly increase signal-dependent (deterministic) jitter, as can poor impedance matching. However, again IME, bandwidth is far and away the biggest culprit, with the caveat that I have not looked at many "audio" cables (mostly data and RF cables designed for 5 GHz and up).

If the signal cannot reach full-scale in a 1-0-1-0... stream, then the physics dictate a longer string of 1's or 0's will shift the zero-crossing and that is signal-dependent jitter.

The interesting thing is that some of the bigger, more expensive cables have higher capacitance and lower bandwidth; designed for looks and marketing, not transmission performance.
 

Phelonious Ponk

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Jun 30, 2010
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Evidently Marlene couldn't afford to test an Audioquest Diamond, or even a lowly carbon. Just as well, at < $200 for 1.5 meters, the carbon is hardly high end.

P
 

mep

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Apr 20, 2010
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So what's the point here? Do high end USB cables increase the sound quality or are they nonsense?
 

fas42

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Jan 8, 2011
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The answer is as for everything in audio: change something and it will normally affect the sound, especially if the system is already working at a high level of "resolution". Whether that change is an improvement or not is up to the listener to decide, and whether the cost/benefit factor makes it worthwhile.

Frank
 

microstrip

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Although I have no doubt about Vincent good intentions when posting these two pictures from this very controversial article, as I already explained him by PM, the real effect was triggering hasty and unfounded comment about poor audiophile practices. IMHO the comment and picture selection can overshadow the apparently interesting but meaningless measurements of the article. As usual the whole picture is much more than a few details. I urge members to read the full article before commenting.

And also to listen to Marlene Dietrich - I decided to look for my recording of Wenn Der Sommer Wieder Einzieht and lsiten to it after seeing the post. Great voice!

PS : For those who enthusiastic assumed the victory of the cheaper cable based only on the noise measurements bellow -110dB : Wellcome to the dark side of audio! :)
 

Phelonious Ponk

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Jun 30, 2010
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Although I have no doubt about Vincent good intentions when posting these two pictures from this very controversial article, as I already explained him by PM, the real effect was triggering hasty and unfounded comment about poor audiophile practices. IMHO the comment and picture selection can overshadow the apparently interesting but meaningless measurements of the article. As usual the whole picture is much more than a few details. I urge members to read the full article before commenting.

And also to listen to Marlene Dietrich - I decided to look for my recording of Wenn Der Sommer Wieder Einzieht and lsiten to it after seeing the post. Great voice!

PS : For those who enthusiastic assumed the victory of the cheaper cable based only on the noise measurements bellow -110dB : Wellcome to the dark side of audio! :)

I don't personally see a victory for either side here, Micro, though I am amused. At a maximum of -100db, no one is going to hear any difference between those cables with music playing.

Tim
 

amirm

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Apr 2, 2010
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Well, I don't think this is what it seems. He used an external USB sound device (SOUND BLASTER LIVE! EXTERNAL USB 24BIT) that is powered through USB. He then captured the analog waveform using another card.

I see a few issues here:

1. A higher-bandwidth cable might make the quality of the power fed to the Soundblaster worse. After all, that is what it will do: pass on more noise from the PC. In a low-power or self-powered USB bridge, the same effect may not be at play at all. The device may use better filtering, etc. and then be helped with the lower jitter aspects of the interface.

2. The use of another sound card to capture opens so many other unknowns. These are not instruments. Further, he didn't run jitter tests. Without that, we don't know what contributions the better cable did in that regard.

Amateur tests like this should be taken with a grain of salt :).
 

Marlene

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Jan 25, 2012
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Well, I don't think this is what it seems. He used an external USB sound device (SOUND BLASTER LIVE! EXTERNAL USB 24BIT) that is powered through USB. He then captured the analog waveform using another card.

I see a few issues here:

1. A higher-bandwidth cable might make the quality of the power fed to the Soundblaster worse. After all, that is what it will do: pass on more noise from the PC. In a low-power or self-powered USB bridge, the same effect may not be at play at all. The device may use better filtering, etc. and then be helped with the lower jitter aspects of the interface.

2. The use of another sound card to capture opens so many other unknowns. These are not instruments. Further, he didn't run jitter tests. Without that, we don't know what contributions the better cable did in that regard.

Amateur tests like this should be taken with a grain of salt :).

I quite agree. This here is my first post here, I´m Marlene, the author of the article Vincent referred to, thank you Vincent.

Another soundcard - even one as good as the Asus Xonar Essence ST - increases the unreliability. That was one of the reasons why I repeated all the tests as much as I did. But I don´t know if they can be repeated on another setups or with other cables (I have to do further tests). As I stated somewhere in my blog, I´m far from being scientific, I also never claimed that to be. I use RMAA, that should say everything about science (NwAvGuy wrote a lovely article about RMAAs' shortcomings). But misinterpreting an article I´ve written also is to be seen with a grain of salt ;)

I didn´t mention jitter tests I did - because they were pointless since jitter didn´t change, it was low in both cases. This card is an asynchronous card and avoids jitter by principle but I "measured" it nevertheless. But since nothing changed I didn´t see the need to publish them.

I also tried a ferrite ring - no change.

I strongly suspect my power supply since the effect of increased noise can only be observed when the soundblaster is connected to the ASUS and not with the loop (though there the distortions are slightly lower). So I assume that something from the power supply is directed through the RCA cable, could that be?

And for anyone who believes that this cable doesn´t change the sound just listen to the examples. The sonic difference is quite apparent. Oh, and the sample excerpts are fully legal (I find this important given the recent attention to things like this).
 

amirm

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Apr 2, 2010
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Oh, welcome to the forum and sorry for my snide remark regarding amateur testing :).

I was pleased that you repeated the tests. I was going to complain about that too until I read that you had done that :).

The issue with a self-powered device is that just pure power delivery can make a difference. If the impedance of the one cable is higher and the device pulls a lot of juice, its performance will suffer especially in low frequencies. This may explain what happened because the output load changed between the two scenarios (loopback and capture with Asus).

I downloaded the file samples but seems like they are in wavpack format and I can't open it with my tools/players. Grrrrr.... :(
 

Marlene

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Jan 25, 2012
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Welcome aboard!

Ground noise and/or coupled supply noise would be potential possibilities...

Thank you. If ground noise or coupled noise are possibilities then which cable represents the truth? In that case it would be apparent that the supplied standard cable rejects noise somehow - the Audioquest does not. How is that done?

Oh, welcome to the forum and sorry for my snide remark regarding amateur testing :).

I was pleased that you repeated the tests. I was going to complain about that too until I read that you had done that :).

The issue with a self-powered device is that just pure power delivery can make a difference. If the impedance of the one cable is higher and the device pulls a lot of juice, its performance will suffer especially in low frequencies. This may explain what happened because the output load changed between the two scenarios (loopback and capture with Asus).

I downloaded the file samples but seems like they are in wavpack format and I can't open it with my tools/players. Grrrrr.... :(

Your snide remarks are more then ok, really! I don´t like criticism... well, I appreciate it anyway - but I do like when someone points out errors in my way of testing, maybe I overlooked something. Always a possibility.

The device pulls the maximum possible energy from the USB hub: 500 mA on all five rails. Windows confirmed that - as did Thesycrons TDD.exe. That means that the Audioquest "allows" more power to be delivered?

You cannot open wavpack? You are on a Linux derived OS then? XMMS can play WavPack files on Linux and Coq can play them on MacOS.
 

microstrip

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May 30, 2010
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Marlene,

Nice to welcome you to WBF. Although I would like to stay away from any discussion on which is the true on sonic aspects, as IMHO there is not a chance that we can correlate these measurements with sound, I would like to point a few aspects. Considering your data I find that the possibility presented by Amir (power issues) more plausible because of the difference in second harmonic distortion between fig3 and 4 of you blog. IMHO only a difference in power can have this consequence. Noise issues are not systematic enough to allow any conclusion.

Just for fun, I have carried a few measurements similar to yours using a single EMU USB 202 tracker and could not find any difference between all my four USB cables, from cheap looking costing less than USD 2 to decent ones as shown in the pictures, but no audiophile USBs. To simulate even worst conditions I even inserted an extra 2m USB extender cable in the system.

I repeated the measurements using a second EMU unit as a source and could see some differences in noise floor between one and two units results, mainly differences due to mains harmonics depending more on cable layout that on cable type. As soon as I moved everything out of my desk, in a floor zone far away from computers and electrical appliances, and optimized the layout, the differences between one or two EMUs vanished.

Please see the attached figures. At the levels we are talking about, in a noisy environment, everything matters.
 

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Marlene

New Member
Jan 25, 2012
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Marlene,

Nice to welcome you to WBF. Although I would like to stay away from any discussion on which is the true on sonic aspects, as IMHO there is not a chance that we can correlate these measurements with sound, I would like to point a few aspects. Considering your data I find that the possibility presented by Amir (power issues) more plausible because of the difference in second harmonic distortion between fig3 and 4 of you blog. IMHO only a difference in power can have this consequence. Noise issues are not systematic enough to allow any conclusion.

Just for fun, I have carried a few measurements similar to yours using a single EMU USB 202 tracker and could not find any difference between all my four USB cables, from cheap looking costing less than USD 2 to decent ones as shown in the pictures, but no audiophile USBs. To simulate even worst conditions I even inserted an extra 2m USB extender cable in the system.

I repeated the measurements using a second EMU unit as a source and could see some differences in noise floor between one and two units results, mainly differences due to mains harmonics depending more on cable layout that on cable type. As soon as I moved everything out of my desk, in a floor zone far away from computers and electrical appliances, and optimized the layout, the differences between one or two EMUs vanished.

Please see the attached figures. At the levels we are talking about, in a noisy environment, everything matters.

Perhaps the results also have to do with other attached device on the same USB hub. I´ve written a new article where I tested my other cables - with interesting results. I´d be curious what you make of this, you seem to be one of the guys I hate with passion: a pure objectivist ;)

Nah, don´t worry, I don´t mean that to embarras you because I also hate pure subjectivists :)

But maybe you do have an explantion, go read it here please: http://marlene-d.blogspot.com/2012/01/more-usb-cables-more-differences.html
 

DonH50

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Jun 22, 2010
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The basic maeasurements appear to be within the error budget of the card so I am not sure you are actually measuring the cables. I have a feeling the shielding on the Belkin is a little worse, and/or it's a little more inductive, explaining the slightly higher HF noise floor.
 

Marlene

New Member
Jan 25, 2012
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The basic maeasurements appear to be within the error budget of the card so I am not sure you are actually measuring the cables. I have a feeling the shielding on the Belkin is a little worse, and/or it's a little more inductive, explaining the slightly higher HF noise floor.

I thought exactly the same - that´s why I repeated the measurments. But I do know that the error margin is higher since I have to rely on soundcards only. Still, the Audioquest and the Belkin both show several tendencies. That´s what I find interesting.
 

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