Friday, 3 May 2013

MUSINGS: "Audiophile" Digital Cables... [Updated November 2013]

As I noted previously, the purpose of going digital has to do with prevention of signal corruption. In doing so,  we can speak of "bit-perfect" transmission of audio data in a way which is impossible in the analogue realm. For example, if we think about the main "container" of consumer high quality analogue music today - the LP / vinyl - nothing can be considered 'perfect'. Each LP is slightly different in terms of being free from warping or (hopefully) minor groove imperfections from the moment it leaves the pressing plant (even the quality of each stamper used varies by generation and age), each time the LP is played, a little bit of damage happens to it so every playback will be different. Even if you keep it in pristine condition, the ravages of time and environmental factors will take its toll on the material itself in large or small ways. Furthermore, there is no way to replicate the music in 'perfect' form as a result (unless you digitize it of course; but only to the quality of the LP playback gear and ADC).

As we know, the CD technology (~30 years old now!) is different. Small imperfections in the plastic or aluminum 'pits' do not lead to audible anomalies thanks to the Reed-Solomon error correction of the digital data. Furthermore "bit-perfect" ripping is routinely done (obviously to the horror of the music industry over the last few decades) and the result is literally innumerably perfect copies.

Let us turn our attention to "digital cables". For some reason, some people seem to forget the above and believe that different digital cables make a difference to sound even when there is no disagreement that bit-perfect data is being transmitted down the pipe in digital form. In fact, there has never been a plausible explanation provided by the supporters of different digital cables. Some talk of jitter being inherently different between cables, some that perhaps electrical noise will disrupt the phase transitions in a digital signal to worsen this jitter and perhaps degrade the bits. But where is the evidence for such beliefs beyond subjective "impressions"?

An industry has developed around digital cables of all sorts. Some of these cables are extremely expensive with price tags of hundreds to thousands. Purported benefits include more exotic / precious conductors, various types of insulation, winding techniques, upgraded connectors. While this is well and good - nobody denies that a well built USB cable with excellent strain relief and connectors that do not break or oxidize is undesirable - why is it that so often audio quality gets thrown into this mix of features during discussions as if it's some kind of 'given'? If a friend says he/she bought a $150 cable that was well shielded, had great connectors, was the right length, and had great cosmetics, I do not believe I would question the motivations since these are all quite reasonable. But if they said "this $150 cable sounds better than all my less expensive ones", I think it would be reasonable to at least wonder about the truth of such a statement just as much as if the friend said "water tastes better from my wine glass compared to just a regular glass cup". Has there EVER been a proven example of a properly functioning digital cable sounding different from another item of the same type?

When it comes to cabling in general, I find it interesting that talk of sound quality is usually propagated by the audiophile press and audio reviewers on-line rather than directly from the manufacturers (see the addendum below for an example of a cable ad). False advertising is a legal offense after all while reviewers spouting off their opinion is given artistic license as subjective experience. This is all fine I suppose so long as it's "above board", but in a small industry where ad revenue is of major importance in the print magazines and web sites, do we really think there is a significant firewall between the reviewers and the source of financial support? A reminder - cables are one of the highest marked up items for any manufacturer. I wonder just what percentage of a cable manufacturer's budget goes into R&D vs. advertising...

Turning to more "objective" matters, let us recap. Over the last few weeks, I measured a number of digital cables of various types in my standard test setup:

USB cables:
http://archimago.blogspot.ca/2013/04/measurements-usb-cables-for-dacs.html
S/PDIF Coaxial cables:
http://archimago.blogspot.ca/2013/04/guest-review-measurements-dr-franks.html
S/PDIF TosLink cables:
http://archimago.blogspot.ca/2013/05/measurements-toslink-optical-audio.html
HDMI cables (updated November 9, 2013):
http://archimago.blogspot.ca/2013/11/guest-review-measurements-quantum-hdmi.html

In each case, using what I had, I tried to "create" improbable setups (eg. very long cables, use of couplers and extenders) which serious audiophiles would likely feel will deteriorate the signal quality. Yet in NONE of these situations was I able to detect an actual loss of fidelity running test signals which have been successful in detecting various types of anomalies over the course of my postings. Subjective listening likewise did not suggest to me any deterioration in sound quality. In contrast, RCA analogue interconnect measurements can be shown to have subtle differences even with relatively short lengths.

What else is there to say, really? In my opinion, there is no other way to interpret the data than to conclude that digital cables of adequate quality to transmit the data in a bit-perfect fashion makes no difference to sound quality. Furthermore, there is no evidence to suggest that the cables influence jitter to any significantly audible degree (again, "jitter" tends to be the scapegoat for almost all digital imperfections for selling hardware). Yes folks, bits are bits as far as the digital cable is concerned. They were engineered to be like this. Over the years I have tried my hand at listening tests with digital cables; but never once have I been able to convincingly differentiate cable quality in any blind testing.

Of course, I could be wrong and open to this possibility...  As usual, if you have good data to show differences between "working" digital cables, please leave a comment.

Enjoy the music...

Addendum:
Here's an interesting advertisement showing "proof" of something (I reproduce this as 'fair use' for the purpose of commentary with no expectation of benefit to myself financial or otherwise):

For the purpose of discussion around just the contents of this ad, I blurred out the company information and trademarked names...  You're welcome to check out the ad found on page 45 of the January 2012 issue of The Absolute Sound (same issue as one of the most disinformative series of articles about computer audio ever to 'grace' an audio magazine from "Dr. Charles Zeilig and Jay Clawson").

1. These cables meet or exceed $20K-$60K competitors' performance. What length are these $20K-$60K cables??? What cables cost this much? Are we talking individual cables or cabling a whole studio? All I can say is throwing a huge number out like that could be either "impressive" or absolutely ridiculous.

2. What is this "patent-pending" XXX Technology? Is it metallurgical? Connector +/- plating? Cable topology? Insulation material? Such a mystery! (To be fair, you can read more about it on the web page to some degree and ponder the claims - go see the ad.)

3. "Nice" plots of square waves I guess...  So it's "absolute proof" that XXX Technology improve rise and fall times of a square wave. We know nothing of the length, type of wire, or even what changed between the "conventional cable" compared to the "same cable" with XXX Technology. Yeah... Nice and "scientific" looking but totally lacking in transparency!

4. What does that square wave plot mean for audio, exactly? Are they trying to say these are digital cables where more precise square wave transitions might imply less timing inaccuracies? But we see analogue speaker spades and XLR connectors (I suppose could be AES/EBU).

5. Notice there's no claims of sound quality. Even the TAS and Rick Rubin quotes say nothing about sound quality, rather something nebulous like "performance". Interesting, given that TAS reviewers commonly speak of comparative sound quality in their reviews of cables yet the company chose not to include such quotes, why?

6. Notice the nice arrows showing directionality of cabling for the speaker spades...  How thoughtful.

Things that make you go... Hmmmmm...

14 comments:

  1. Nice commentary Archimago. Things that indeed make you go HMMMMM!

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  2. The particular VA100P5 is usually an 10 wall plug universal transitioning power. It could possibly offer 5V DC with nearly 8A for you to switch on for you to 10 Kramer solutions of which make use of an external 5V DC power.
    http://www.dueltek.com.au/collections/power-distribution-units/products/va-100p-5-kramer

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  3. After auditioning several high priced coaxial cables it became obvious for me that coaxial interconnects DO differ in how they deliver audio results between components. After testing Signature top level cables, I constantly notice repetitive difference even in Silver audiophile grade coaxial cables. My undisputed winner is Malbru Silver CX coaxial cable that constantly brings a much thicker and deeper sound, I think its hard to bit it, you should find them on Amazon. So auditioning is a MUST for selecting good quality coaxial cables and you need to get a good one as it helps your source to really open up to the extend that cables allow, so no short cut here, quality audio coaxial cables cost money and they are absolutely worth it if course if you want to squeeze the maximum form your DAC.

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    Replies
    1. Of course you're going to make such unsubstantiated claims considering you're in the snake oil business selling silver USB cables costing upwards of $400usd. It only took 30 seconds to find you using Google.

      https://twitter.com/mykhailo_m

      As well as where you peddle your snake oil...

      http://malegaaudio.com/

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  4. The new crop of audiophile network cables for media servers makes me wonder. There is the fact that a media server will reduce stream quality if it runs into issues talking to the client, but it really shouldn't be happening on a home network.

    Your comment about CDs reminds me of a test I did many years ago. I had heard that copying a 'stamped' CD onto a writable one could improve the sound performance. To my surprise, it did - at least in my test. Not in a subtle way, either.
    I have tried to tell many of this, but the deniers won't try it as it can't possibly happen. But it did. The best explanation I can find is due to a recent trip to Wikipedia on my part. Apparently Reed-Solomon only works as long as the reader's head can track the disc properly. If not, it doesn't work.
    I have seen many CDs where the hole punched in the centre does not correspond with the centre of the data tracks. Maybe this is the reason for an impossible situation becoming possible.

    Perhaps digital cables also have effects under certain circumstances we're not aware of yet...?

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  5. Most USB cables have two types of connectors, one on each end. A type A connector is on the end that plugs into your computer. These are wide and flat, with a plastic piece inside that prevents the user from plugging them in upside down. Most users are familiar with the type A USB ports on their computers, as virtually every peripheral device on the market these days uses them. For instance, printers, scanners, and digital cameras all connect to computers via a USB cable. USB drives, which are small, mobile data storage devices, usually have type A connectors on one end, which plug directly into the USB ports on a computer.
    I’m pretty tough on my cables and I would bet that these cables would take a beating and keep on working.

    This is only a really light look at all the great USB products at CES 2017. I was personally amazed with the scale of USB product promotion but it makes sense, USB products are multi-billions of dollar business and everyone wants a slice of the pie.

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  6. Thanks for the post. Im a big fan of the blog.!!

    electrician

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  7. Unfortunately I don't know English, so I called the google translator for help. It may not give back well what I want to communicate.

    And then here is my writing:
    I don’t have systems in the millions, unfortunately: probably if someone gives me 100,000 for a 1m USB cable, their DAC, amp, and speaker are at least a few million.
    I also sign that cables play a big role. Especially for an analog signal, but for a digital signal, I think there are exaggerations; and now I'll tell you what I think.
    I LOOK FORWARD to someone’s convincing response to the opposite of my sentences. If this is not the case, the hanky-panky of digital cables will remain above a certain level for me.
    And then my text: so if I transfer a file over cable, wifin or bluetooth from one source for one purpose, it can’t happen that that digital signal set is even 1 bit different. That's obvious! From now on, no IT sign would be reliable, so this text, for example, would not be reliable. It wouldn't work well if this "1 bit" text says "2 bit" or looks like "0 bit" due to a 1 bit difference. In both cases, there was only one bit difference in the bitmap of the string. But here's another case for a 1-bit difference: "1! Bit" (check out the ASCII bit sequence for characters here if you don't know: https://en.wikipedia.org/wiki/ASCII)
    I continue...

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  8. This comment has been removed by the author.

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  9. This would be even more critical for executable files, as it could result in bad code that would not even run the program / application. But it is also not permissible, albeit a little exaggerated, for me not to be in a printed image, but, say, a cat; oh well it's maybe rough, let's refine it: don't let a black hole open in the place of my eyes. Well, that's rough, too, let's refine: let's just have a few pixel errors.
    So in the case of sound, some kind of sound defect corresponds to the pixel error of the image. But there is no pixel error on the printer either !!! If so, it's not because of the USB cable, because it wouldn't be allowed, as we've already looked at above. Not all cartridges may have enough color, paper jams or cartridge clogging, or other mechanical defects. But it has nothing to do with the data content on the USB, since then the hell ate the signal!
    What do they do when transmitting signals? I’m not an expert, but they use data packets and checksums for them that ensure the integrity of the data packet, in other words, to make the source string match the target string.
    And now I have reached the end of what I have to say. WHY IS IT NOT POSSIBLE TO ENSURE THE INTEGRITY OF THE DIGITAL SERIES WITH THE AUDIO SERIES LIKE ANY OTHER SERIES ?! It doesn't matter if the different devices and cables transmit an image sequence, an email, a pdf, or just some audio format: they don't know until we tell them at the end point when they need to decompress and convert it.
    So for AUDIO SERIES, why not use a similar checksum solution ?! That is, it does not capture the signal until it arrives unscathed, as is the case in the other cases. This would solve this problem.
    I understand that time has a role to play, but buffering has long been invented and is also used by audio player software. So if such an accurate signal were stored in the DAC and stored on the original source (CD or file; all the same), the 100 digital cables would be over! Because we can also send the exact signal to the printer with a few hundred forints cable. Although there may be a lot of error-correcting communication that takes time, if we use a few thousand forints of cable, it can be faster.
    The question here is no longer whether the signal sequence is coming through well, because a bad signal cannot come through !; but the question is whether the cable is in a technical condition that is suitable for data transmission. If appropriate, the applicant should be able to resolve it. If the cable meets the minimum requirements (which is an engineering cliché minimum), there can be no bad signal on the receiving side because the question will be whether the cable is suitable or not. Better quality may play a role in the need for fewer repair algorithms -> so fewer buffers may be needed -> so there is no risk that the timing of the music playing will be "chunky". With a sufficiently large buffer, in my opinion, the same result can be achieved with a lower quality cable, since: THERE CAN BE ANOTHER SIGNAL ON THE RECEIVING SIDE OTHER THAN THE SOURCE SIDE!
    That's my opinion! I am convincing, but it is very difficult in this matter! 🙂

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  10. Well, finally! I found a technically sound answer that was relevant to me, not incidental.
    Someone linked, but I may have found it: here

    "Stream Pipe: This form of USB pipe is uni-directional and it is connected to a uni-directional endpoint that transfers data using an isochronous, interrupt, or bulk transfers (see below)."

    "Isochronous: This form of data transfer is used to stream real time data and is used for applications like live audio channels, etc. It does not use and data checking, as there is not time to resend any data packets with errors - lost data can be accommodated better than the delays incurred by resending data. Packet sizes can be up to 1024 bytes."

    There seems to be no time to check the correctness of the packet for real-time reception of large amounts of data, so the one-way connection should be so perfect that the data packet sent and traveled once (without a correction algorithm) is approximately the same as the source data packet.

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