Yes, same for AES/EBU.
I would not be surprised if cable designers do in fact lack knowledge. There’s one well known cable company that sells a digital 110 ohm cable, terminated in RCAs, which is way off base because SPDIF protocol calls for a 75 ohm cable while a 110 ohm cable is an AES/EBU cable and there you use XLRs .
I had had another cable drop shipped to me direct from the manufacturer that simply did not work- no continuity in the center pin.
Another cable - an XLR, from yet another manufacturer, developed an intermittent short. Upon closer inspection, it was clear the workmanship in connecting the XLR was quite substandard.
I’ve experienced RCAs without any real strain relief eventually leading to a broken connection.
I would rather ther consider the opinion of an EE doing digital work vs someone who buys reels of Mogami or whatever cable, puts on some techflex, gets some heat shrink with a company name printed on it, and does in house terminations, because I’ve come to think many cable companies are no more than just that, just repackages. At least Blue Jeans cables is utterly transparent about that.
I would not be surprised if cable designers do in fact lack knowledge. There’s one well known cable company that sells a digital 110 ohm cable, terminated in RCAs, which is way off base because SPDIF protocol calls for a 75 ohm cable while a 110 ohm cable is an AES/EBU cable and there you use XLRs .Yes, that could very well reflect lack of knowledge, but another possibility that wouldn't surprise me is that it was done intentionally, to make that cable sound as different as possible than the competition. My perception has been that it is not uncommon among audiophiles for "different" to be perceived as "better," at least in the short term, even if it isn't. And as Steve wrote in this paper regarding jitter, which would presumably be the main consequence of this kind of impedance mismatch:
I remember the original threads and article claiming this and had bounced it off a very sharp engineer friend of mine at the time and several others. In short, I don't believe it is true; there are more than a few high-quality SPDIF and AES cables on the market which test out perfectly at 1.0 meter.
It depends on the transition time. 1m might be perfectly fine with transports that has 15ns transition times. In addition, reflections appear only on impedance boundaries. With a perfect match (rare) there will be no reflections. Very short cables, under a foot, will also work fine. Rule of >1.5m is just for general case of typical transport.
Jitter is basically an added noise. Music free of noise might sound clinical and sterile at first. One person even posted, after listening to jitter supressing DAC, that he preferred all instruments "together" (sound blob) instead of hearing individual instruments. Also, music with added noise can sound more dynamic - like distorted guitar vs clean Jazz guitar. I believe that jitter destroys everything, but we tolerate it since we got used to it.
I remember the original threads and article claiming this and had bounced it off a very sharp engineer friend of mine at the time and several others. In short, I don’t believe it is true; there are more than a few high-quality SPDIF and AES cables on the market which test out perfectly at 1.0 meter.As is explained in Steve’s S/PDIF article to which Zavato provided a link, what length will be optimal is dependent on the risetimes and falltimes of the signal provided by the component which drives the cable. (Risetimes and falltimes referring essentially to the amount of time required for the signal to transition between its lower and higher voltage states, and vice versa). Those parameters are rarely if ever indicated in the specifications of digital audio components.
Several other factors are also involved, including the happenstance of how well the impedances of the cable and the two interconnected components match, the propagation velocity of the particular cable, the susceptibility of the particular components to ground loop issues, the jitter susceptibility of the particular DAC, etc.
So there is obviously some unpredictability that is involved. But as someone who has also on occasion been alleged to be a sharp engineer :-) I would consider Steve’s recommendation of 1.5 meters to at the very least provide the best odds of being optimal.
This assumes, btw, that a very short length, such as say 6 inches, is not practicable. In circumstances where it is practicable, I suspect it is likely to be an even better choice than 1.5 meters.
Edit: This post was written before seeing Kijanki’s post just above, with which of course I agree.
Speaking of digital, several years ago a buddy came over to hear my system , listened a while and got up and pulled the power-cord from my internet modem/router . Sound went from very good to live music !
Also put a heavy blanket over my TV which was not near the system. Not as big a deal but a slight difference .