Jitter and 75ohm cable length

Thank you Al, and thanks for the links especially the second one. I suspect that balanced cable might be superior in noise rejection simply because of common mode rejection on the receiver side but also because wires are twisted what might be superior to any shielding. Twisting wires exposes them evenly to interference (capacitive or electromagnetic) leading to cancellation while shielding have serious limitations. I mentioned it before, but non magnetic shielding does not protect against EMI (magnetic in nature) but fortunately induced noise travels (to ground) on the outside of the cable - shield, because of skin effect. This beneficial skin effect is good at high frequencies but less than perfect at the lower frequencies where cable is still long enough to become effective antenna (antenna is practically ineffective below 1/10 of wavelength). Understanding of this should lead to understanding that shortest cable is the best cable. Statement that digital cable should be at least 1.5m is not complete - it should state instead "as short as possible but not shorter than 1.5m". In ICs (or speaker cables) twice shorter means twice better. Sales people often recommend 1m IC vs 0.5m IC because that's what they have in stock - absolutely no other reason.

Can someone here give me a hand with the math and it's implications with respect to two different cable lengths from the exact same manufacturer. Much of the math in this forum is in meters, the typical standard. One of my cables is 3' in length and the other 6' in length and strangely they sound different. Specifically, the 3' cable sounds very fast slightly bright (or hyper detailed) where the 6' cable sounds a bit warmer, maybe slightly rolling off the top, or maybe just cleaner at the top. I've talked about these cables earlier choosing the 3' cable as the champ, but now I'm finding the 6' cable easier to listen to. How can this be explained and may the 6' rout look better on paper and on the ears - thanks!
Rpg

Rpg, 1 meter is about 39.37 inches. And of course 12 inches = 1 foot.

Therefore 3' is about (12 x 3)/39.37 = 0.91 meters, which DOES NOT conform to the length recommendation.

6' is about (12 x 6)/39.37 = 1.83 meters, which DOES conform to the length recommendation.

I've talked about these cables earlier choosing the 3' cable as the champ, but now I'm finding the 6' cable easier to listen to. How can this be explained and may the 6' rout look better on paper and on the ears.

Chances are that less jitter is present with the 6' length, but as explained earlier that is not a certainty. Also, as explained in the section entitled "Jitter Correlation to Audibility" in the Steve Nugent paper I linked to a few posts above, depending on its spectral (frequency) characteristics jitter can sometimes be euphonic in character, and/or mask or compensate for inaccuracies elsewhere in the system.

So the bottom line obviously is to try to decide based on listening, but I would say that if the cables sound different but neither can be determined with confidence to be "better," chances are it would be best to go with the longer one.

Regards,
-- Al

Al, thanks, I appreciate your work in helping me understand this. I think in the end, as I may have mentioned, the 6' cable is easier on the ears. With this cable manufacturer, I can order any length, is there an "ideal" length, or are there too many system dependencies to determine this?

Again,
Thanks!

With this cable manufacturer, I can order any length, is there an "ideal" length, or are there too many system dependencies to determine this?

Summarizing all that has been said, I would put it that a length of 1.5 meters (which is virtually the same as 5 feet, to within less than an inch), stands a better chance of being ideal than any other length. But as have been cited there are many system dependencies and cable type dependencies which conceivably could result in other lengths being better in some cases.

In this case, if you decide that the 6' cable you have is preferable to the 3' cable, my suspicion is that changing the 6' cable to a 5' cable of the same type would be unlikely to make a significant difference.

Regards,
-- Al