Length of SPDIF cable

Longer is better for SPDIF cables! Signal reflections in shorter cables can interfere at a DAC’s input receiver. I bought a 1 meter and a 1.5 meter SPDIF cable. I am using the 1.5 meter into a DAC. You can try your 1 meter. It may work fine! Companies should just make 1.5 meter and longer SPDIF cables. They are catering to the audiophile belief that 'shorter is better'. The metal type (copper or silver) doesn’t matter. As the French chef says " No diffawrance!"

I have a 1M SPDIF,  and it works just fine, I haven't heard of the 1.5M being the ideal length. But YMMV.

I think the value of a long SPDIF cable is exaggerated. the logic assumes the whole circuit is a perfect 75 ohm system. It ignores the connectors, the wires inside the components, the circut boards inside your DAC, etc.

On an unrelated note, the salesman doubles his profit on a longer cable.

Jerry

Apparently this whole thing about longer spdif cable length (and it was common to also use 1.23 and 1.25) being better was due to the 1990’s spdif receiver chips in older DAC/transport combos being susceptible to cable reflections.

It’s not supposed apply anymore, but considering what a race to the bottom a lot of modern equipment is built like, maybe it does?

Al, (Almarg...R.I.P. my friend) always said that a coax digital cable should be 6-8 inches or 1.5M (60 inches).

I have followed his advice.

Man, I really miss him...

Big +1 @mofimadness 😔

The brand is more important than the length. If you have $100K components… and the very best interconnects, then I would start worrying about the exact length. 

The best SPDIF cables are made from wire drawn from 16th Century Japanese silver ingots by blind monks!

I know that Nordost recommends 1.5 m but I haven’t personally heard a difference between 1.5 and 1m. I’m skeptical about these type of things that are not noticeable to your ear. I suppose you could tell a difference if you compare based on measurements alone but not actually hearing a difference. Now, the balanced vs unbalanced issue with analog interconnects and length causing hum is another story.

@jasonbourne71 

Ok, that was a good one. 👍

Beginning of transition of digital signal creates reflection from the mismatched characteristic impedance at the end of the cable. This reflection comes back and adds to original transition distorting its shape and causing possible time shift of threshold point, resulting in jitter. Typical transition is likely 25ns while signal travels at about 5ns/m. With 1.5m cable signal will come back in 2x1.5mx5ns/m=15ns, just missing half of transition (likely threshold point) at 25ns/2=12.5ns.

It assumes 25ns transition and 5ns/m signal propagation while real life values can be way different. Transitions can vary 5-50ns while signal propagation depends on cable dielectric. I would feel safer with >2m cable.
It is also possible that there are no reflections at all (good impedance matching) or that DAC has good jitter suppression.

Cable becomes transmission line (possible reflections), when signal travel time one way is longer than about 1/8 of transition time. With 25ns it comes to about 3ns equivalent to 0.6m (at 5ns/m). This value includes internal wires and PCB traces at both ends. Even 1ft wouldn’t be very safe IMO, so I would go for mentioned 6-8". In this case shorter is better.