Why do digital coax cables matter?

Almarg wrote,

"The 1.5 meter length recommendation that is often seen for digital cables has no relevance whatsoever to cables conducting analog audio signals. In general, in the case of analog audio cables the shorter the better, if it makes any difference at all."

>>>>>That’s weird. Most high end cable manufacturers with good hearing like Bob Crump recommend 1.5 m as the optimum length for interconnects, maybe for speaker cables, too. I suspect the same is true for digital cables since they’re all conducting electromagnetic waves, so what’s the diff? Certainly the particular metal, copper or silver or gold infused silver, in a digital cable, like interconnects, is audible so why not the length? My personal favorite reason is that 1.5 m minimizes reflections. Al, I'm confident you will come up with a perfectly valid technical reason why length cannot possibly be an issue for analog cables, and why audiophiles must be imagining things.

Geoffkait 8-30-2017
... so what’s the diff?

The difference is the frequencies that are involved, Geoff, which bring completely different effects into play. Such as the one that is explained in the paper by Steve N. of Empirical Audio that was referenced earlier in the thread, which explains the rationale for 1.5 meter digital cables. That rationale having no relevance whatsoever to analog audio signals, since it involves the effects of signal reflections that result from impedance mismatches at RF frequencies on timing jitter at the point of D/A conversion. Surely you realize that cable effects can be dependent on frequency, especially when both the frequencies and the application are vastly different? If you don’t, any further debate would be pointless, and I’m not going to engage in any.

Also, your last sentence represents a complete misreading of what I have said. I absolutely did not say, and have never said in this thread or any other, that length differences in analog cables won’t be audible. In fact in many other threads, such as this one in which you’ve participated very recently, I’ve said that they certainly can be audible. I have said, however, that in general the shorter an analog cable is the better, assuming the goal is for the signal to be conveyed in as accurate a manner as possible (i.e., for the sonic effects of the cable to be minimized).

Feel free to have the last word, even if it involves asserting that something I have neither said nor implied is incorrect. To others who may be interested in the subject, I would commend the excellent posts earlier in the thread by Kijanki, AudioEngr (Steve N. of Empirical Audio), and others, as well as my own posts.

Regards,
-- Al

Sorry Al, don’t buy it. You get an E for Effort. I won’t point out your name dropping. You apparently haven’t had the opportunity to try the Shun Mook Orignal Cable Jacket or the Highwire Cable Wrap, both of which improve the sound of *analog* cables by, you guessed it, addressing the cable reflections. I know what you're thinking, "But, but that disobeys the laws of science!" 😀

cheers

People would be much better off if they believed in too much rather than too little. - PT Barnum

I won't pretend to know much of the scientific facts about cables and I maybe over simplifying this, but doesn't cable inductance have a large effect on a cables sound. Inductance is affected by length, isn't it???

Mr_m, yes, inductance and most other cable parameters are proportional to length, including resistance, capacitance, the resistance rise at high frequencies caused by skin effect, the effects of dielectric absorption, and propagation delay.

In the case of analog cables, inductance is most likely to be audibly significant in speaker cable applications, especially if the impedance of the speaker is low at high frequencies (as it generally is in the case of electrostatic speakers), and/or if the cable length is long, and/or if the particular cable has relatively high inductance per unit length. The impedance presented by an inductance is proportional to frequency, and therefore in the upper treble region may become an audibly significant fraction of the impedance of the speaker in those situations.

Inductance (as well as resistance) will usually be unimportant in the case of line-level analog interconnects, since the corresponding impedances will be vastly smaller than the input impedance of the component receiving the signal. In that application capacitance will often be important, particularly if the output impedance of the component providing the signal is high.

In the case of digital cables, inductance is one of the key determinants of what is called "characteristic impedance," which for coaxial S/PDIF is nominally the 75 ohm figure you are probably used to seeing mentioned, and for AES/EBU is nominally the 110 ohm figure you are probably used to seeing mentioned. The characteristic impedance of a cable is NOT proportional to length. However at the RF frequencies which comprise digital audio signals the less than perfect impedance match that will inevitably exist to some degree between the cable’s characteristic impedance and the nominally 75 or 110 ohm impedances of the connected components will result in some fraction of the signal energy reflecting and re-reflecting back and forth along the cable. The arrival of those reflections and re-reflections at the DAC will result in some degree of distortion of the signal waveform as received by the DAC, which may or may not ultimately affect timing jitter at the point of D/A conversion, depending on the arrival times and also on the design of the particular DAC. And those arrival times will be dependent on the length of the cable as well as on the propagation velocity of the particular cable. That is explained well in the paper by Steve N. of Empirical Audio that was linked to earlier.

Regards,
-- Al

The more things change the more they stay the same. This whole discussion is a rehash of what was said in the early days of this thread five years ago. In fact, it’s a rehash of the cable controversy that started what, 40 years ago? All you need is zip cord or something like that. And technical types were claiming the laws of physics were being broken back then, too. "There are only 3 things that can affect cable performance, resistance, capacitance and inductance." Yeah, right.

I stream TIDAL hard wired CAT6 from my 5G modem to my 16 bit capable Apple TV connected via Audioquest Coffee HDMI cable and I still think my system sounds great.  However, I have recently decided to purchase a Bluesound so I can take advantage of TIDAL's hi res subscription.  I just hope I can hear the difference between 16 and 24 bit.

The retailer suggests I connect the Bluesound to my ARCAM AVR550 using Audioquest DC powered Coffee digital coax at a cost of $429 for just a 1 meter cable.  Since the Bluesound costs $499, this digital cable will cost about the same as the Bluesound.  I got cold feet over the weekend and told the retailer to order the Audioquest Carbon digital Coax at a price of $192.  I'd be curious how many feel I am making a big mistake or is my assumption downgrading the cable from Coffee to Carbon is not to make any difference in sound quality?

Also, I have looked at music streamers ranging in price from $499 to $1,600 to include Bluesound, Roon and Bel Canto music streamers.  Is there a significant difference in sound difference between them?  From what I can determine the DAC inside my ARCAM is better than the DAC's inside all three music streamers.  I think the real difference will be to add a DAC that is capable of unfolding MQA completely.  Unless, these players can either unfold 10x from the MQA data, they can really only unfold 1x, which then plays down to 16/44, the same as a 16 bit CD.  Also, why we are at it, can you really hear a difference between MQA played through an MQA certified DAC VS 24/192?  If not, they I am questioning whether I should switch from TIDA to Qobuz which streams at 24/192.  Seems to me like 24/192 sounds better than MQA anyways.