Is a S/PDIF coax cable longer than 1m better?

[Empirical Audio]

See my white-paper:

http://www.positive-feedback.com/Issue14/spdif.htm

We can argue til the cows come home about the signal risetime and whether this is really necessary, but I have verified it using a 400psec risetime device when doing jitter measurements. (Most S/PDIF outputs are much slower than the gear I design, more like 4nsec) I either have to connect the device directly to the scope or through 1.5m cable in order to avoid adding more jitter. It shows up in the plots and the numbers.

Attached is one independent A/B test, albeit not controlled, that confirms my claims that 1.5m is better than 1m or 0.5m length.

 

[thomask]

I had been happy with 1.5 m Zenwave D4 digital cable which seems to have more detail than 1m digital cable.

But 1.5m one is shielded and 1m cable is unshilded.

I am not sure whether shielding also contribute more details or not.

 

[Empirical Audio]

Unshielded digital cable? How do they get the 75 ohms impedance????

 

[DaveC]

Unshielded digital cable? How do they get the 75 ohms impedance????

IDK, there's a formula for characteristic impedance somewhere, eh?

All I can say is my S/PDIF cable has been preferred over every single cable it's EVER been compared to, and is a far superior design vs a coax. The proof is in the demo and I'm more than happy to have anyone who doesn't own a cable business (current or previously) to try it out, just let me know via PM here or dave@zenwaveaudio.com.

BTW I do agree with making the S/PDIF cable 1.5m + and I don't offer shorter cables anymore. I'm in the process of building another more up-to-date website...

 

[Empirical Audio]

If it's that good, I can do jitter measurements on it here and provide those to you.

I used to make a twinaxial coax cable for S/PDIF myself, but replaced it with an aerospace grade coax.

 

[Sablon Audio]

Unshielded digital cable? How do they get the 75 ohms impedance????

My spdif is unshielded and non-coaxial, being arranged with what Townshend now market as fractal geometry (basically twisted pair with different size conductors). You need to crunch some maths to arrive at a theoretical 75ohm, using conductor sizes and spacing / dielectric constant and thickness / twist spacing and the calculated outcome was well within the spdif spec’s tolerance parameters. That said, there’s a fair chance that the equipment jacks and internal wiring won’t be 75 ohm compliant.

The sonic outcome was that it beat the $3700 reference cable owned by Terry London and he bought mine instead.

In the context of this review, I would also like to share another amazing find regarding a digital cable. My reference cable for over five years was the amazing Stealth Audio Sextet that retails for $3,700. During the review process for the Zdac, I also auditioned the new Panatela digital cable, which retails for $475, from Sablon Cables. The designer/owner Mark Coles has produced the finest-sounding digital cable that I have ever reviewed for its remarkable price. The Panatela cable replaced the Stealth Sextet to become my new reference and was used to review the Zdac.

 

[Sablon Audio]

Every day is a school day they say, and that was certainly the case for me quite recently when a customer pointed out that the Atlas BNC plugs I had been using for several years looked like 50ohm instead of the 75ohm they were marketed as.

So I decided to make lemonade from my remaining stock of these lemons by pressing out the insulation and mechanically modifying it to 75ohm spec. I also took the opportunity to cut out the monkey metal contact pin and drilled out the wire holder so that the wire itself can be pulled out to replace it and penetrate the chassis jack directly without any impedance discontinuities or inferior materials/solder in the signal path. There was a pretty pleasing delta from these changes.

 

[Empirical Audio]

Every day is a school day they say, and that was certainly the case for me quite recently when a customer pointed out that the Atlas BNC plugs I had been using for several years looked like 50ohm instead of the 75ohm they were marketed as.

So I decided to make lemonade from my remaining stock of these lemons by pressing out the insulation and mechanically modifying it to 75ohm spec. I also took the opportunity to cut out the monkey metal contact pin and drilled out the wire holder so that the wire itself can be pulled out to replace it and penetrate the chassis jack directly without any impedance discontinuities or inferior materials/solder in the signal path. There was a pretty pleasing delta from these changes.

Actually, not all 75 ohm BNC's have no insulator in the barrel. Some do and it's usually smaller than the 50 ohm version.

 

[Sablon Audio]

Oh this plug came with a full length insulator Steve so it was pretty clear that it was really 50ohm rather than 75.

 

[Empirical Audio]

My spdif is unshielded and non-coaxial, being arranged with what Townshend now market as fractal geometry (basically twisted pair with different size conductors). You need to crunch some maths to arrive at a theoretical 75ohm, using conductor sizes and spacing / dielectric constant and thickness / twist spacing and the calculated outcome was well within the spdif spec’s tolerance parameters. That said, there’s a fair chance that the equipment jacks and internal wiring won’t be 75 ohm compliant.

Calculated and actual are sometimes different things. I could evaluate this cable on my jitter measurement system. If It's that good, it should not add any visible jitter. My aerospace quality coax doesn't:

https://www.audiocircle.com/index.php?topic=154425.0

BTW, all of my products have 75 ohm silver coax inside and 75 ohm BNC on the panel. This is the kind of signal you get with that:

 

[Sablon Audio]

Thanks Steve but I’m not sure that there is any upside in my sending you a cable to measure. It sounds excellent as things stand and that is all that really matters.

 

[Empirical Audio]

Oh this plug came with a full length insulator Steve so it was pretty clear that it was really 50ohm rather than 75.

Neutrik makes a really good 75 ohm BNC plug.

 

[Empirical Audio]

Thanks Steve but I’m not sure that there is any upside in my sending you a cable to measure. It sounds excellent as things stand and that is all that really matters.

My older twinaxial S/PDIF cable sounded really good too, but not as good as my current coax. The measurements taught me that having silver for both center conductor and shield is important for SQ, but it does not show up in the measurements. Again, the measurements are woefully inadequate to fully characterize what we are hearing.

BTW, do you audibly determine the directionality of your cables and then mark them?

Do you have a theory as to what is going on there?

 

[Sablon Audio]

Thanks for the Neutrik tip and we can agree that not everythng that matters measures!