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In Reply to: RE: BNC and SPDIF posted by ahendler on January 24, 2016 at 11:18:00
And I have found a digital coax cable with RCA plugs will sound better when installed in one direction compared to the other. Especially coax cables with solid core center conductor.
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Perhaps a directional wire issue, or a variation of termination at either end of a digital cable, which may produce different reflection characteristics thus different sonic signatures? This may also include the use of different make/model digital I/O jacks from source to load, which must in some way contribute to the 75 ohm characteristic impedance of a digital interface... my 2 cents
Quote from Stereophile article Link:
Page 3
Measurement surprises
I had planned to try measuring jitter differences in digital interconnects only after I'd finished measuring transports. If there were measurable differences in cables, I thought they would be revealed only by averaging many measurements with each cable (to reduce the influence of random noise), and then processing the data to uncover the tiniest of differences. The System One has a "Compute Delta" function that extracts only the difference between two measurements. My preconception was that any measurable differences between different coaxial digital interconnects would be marginal at best.
Continued on page 4
After measuring the first two products (the PS Lambda and the Panasonic SV-3700), I went back and repeated my measurements to make sure the analyzer was giving consistent results, and that my test setup was correct. When I remeasured the SV-3700, I got about half the jitter than when I first measured it!
What caused this reduction in measured jitter?
Changing the direction of the digital interconnect between the transport and the jitter analyzer.
This phenomenon was easily repeatable: put the cable in one direction and read the RMS jitter voltage, then reverse the cable direction and watch the RMS jitter voltage drop. Although I'd heard differences in digital-cable directionality, I was surprised the difference in jitter was so easily measurable—and that the jitter difference was nearly double.
To confirm this phenomenon, I repeated the test five times each on three different digital interconnects. One was a generic audio cable, the other two were Mod Squad Wonder Link and Aural Symphonics Digital Standard, both highly regarded cables specifically designed for digital transmission. The generic cable wasn't directional: it produced the same high jitter in either direction. But both the Wonder Link and the Aural Symphonics had lower jitter levels overall, but different jitter levels depending on their direction. Moreover, the generic cable had higher jitter than either of the two premium cables—even in the latters' "high-jitter" direction.
And then this,
I performed the same tests using the low-jitter PS Audio Lambda transport as source. The results were very different. With a good source, cable direction didn't make a difference in the measurable jitter (fig.10). This suggests that the SV-3700—or any poor-quality transmitter—reacts with the cable's impedance to create jitter-inducing reflections in the interface. The directionality was probably caused by differences in the way the two RCA plugs were soldered to the cable; any bumps or discontinuities in the solder or RCA plug will cause a change in the characteristic impedance, which will cause higher-amplitude reflections in one direction than in the other. These reflections set up dynamically changing standing waves in the interface, introducing jitter in the embedded clock. These problems were reduced by the Lambda's higher-quality output circuit.
Was it the only reason? Maybe.
The directionality was probably caused by differences in the way the two RCA plugs were soldered to the cable; any bumps or discontinuities in the solder or RCA plug will cause a change in the characteristic impedance, which will cause higher-amplitude reflections in one direction than in the other.
What ever the reason I have found Digital coax cables with RCA plugs are directional regardless what the manufacture of the digital cable might say. Even those with arrows should be listened to in both direction to hear which way sounds best.
Jim
Another issue to consider:
Cable burn-in affects the relationship of the dielectric and the conductor. Even if the wire implemented for a particular cable is not directional from a metallurgy annealing process POV, the dielectric tends to become directional when fully burned-in while pointed in the same direction. So if the direction of the cable is then reversed, the presentation may sound quite different than before, perhaps with readily identifiable sonic signatures. A second substantial burn-in process tends to be beneficial for the new orientation, although substantially quicker to complete than the initial direction tends to be. As such, one can't know what direction may sound better, which one (or both) may stand the test of time unless plenty of time is given to both directions burn-in cycles.
I have a Blue Jeans 1694a with Canare RCA on one end and and BNC on the other. I use it from my Gustard U12 reclocker (RCA) to the BNC input of my Audio-gd Master 7. It is an excellent cable.
Gustard is an excellent bargain. My new Gustard DAC-X12 is a very high-performance ESS Sabre32 DAC for under $500. I've been swapping out several 75 ohm digital coaxial cables, and the DAC presents the various sonic signatures of the digital audio cables very coherently, including when the direction of the various cables are reversed (plugged-in "backwards"). It would be nice if the Gustard DAC-X12 featured a remote control function for volume control, since the ESS DAC chip offers non-detrimental digital volume control adjustments.
Interesting read. Years ago I switched from a Cal Delta to a PS Audio Lambda and differences in sound quality were easy to hear.
My belief is that everything has an effect on the sound of digital, the transport, cable, and the dac. There was a time when people thought that any CD or DVD player was acceptable when used as a transport.
Now it is usb cables and jitterbugs, that are being questioned.
That's just my opinion though.
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