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Can anyone comment on the good the bad and the ugly with making a cable with BNC on one end and SPDIF on the other? This is for a digital application going from an network renderer and a DAC.
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No problems. Many cable manufacturers make digital cables with the option of different terminations at either end.Many things are commonly overlooked :
1. Cable Impedence.
75ohms is the characteristc impedence of the specified S/Pdif interface. Note characteristic. It is important when very long runs of cable are used . For the very short lengths used for digital connections in home systems it is not as significant when using typical co-axial cables.2.BNCs are 75 Ohms.
No they are not, at least the ones we see most of the time. Their properly specified impedence is 50/75 Ohms. The only true 75 Ohm BNC I am aware of is made by Canare. It is physically different to the 50/75 Ohm ones as it seeks to maintain the same spacing between conductor and dielectric from the entrance to the receptacle to the actual terminals (if the spacing is lost then so is the characteristic impedence)3. The interface's impedence characteristic is not usually maintained from transmitter to the receiver in practice.
The DAC has, for example, a BNC chassis mounted port. However look inside the DAC. In most cases this is port is then just connected to some hook up wire of indeterminate spec. and the S/P dif receiver is then connected to this. Fortunately the length of the hook up wire is very short. But the theoretic "75 Ohms" is lost nevertheless.4. The S/Pdif" interface specifies a BNC connector.
No it doesn't. It specifies the characteristic cable impedence. In fact if you ever see the original red book (which incorporates the basic spec for what subsequently became known as SP/dif) it illustrates the interface using an RCA connector.5. Directionality.
I have never come across a digital cable that doesn't sound preferable in one direction over the other. At least as important as all other considerations.So, just do what you need to connect your boxes together.
BTW, BNC/RCA Adaptors: Even if you think that they sound fine when installed they quickly degrade (oxidisation? Just general crap?). So disconnect them and re-install frequently to keep them clean. some of the adaptors ( e.g. as used by Black Cat or Nordost) actually sound pretty good. Other types I will leave open to your experimentation.
Edits: 01/26/16 01/26/16
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Just so happens that this thread posts about BNC/SPDIF including measurements ... http://www.stereo.net.au/forums/index.php/topic/92685-why-digital-seems-to-be-affected-by-power-and-cables/page-6
Edits: 01/24/16
Have you tried a bnc to rca adapter?
I had to use one with a I believe it was an Audio Alchemy jitter box. I don't recall it being a problem and the adapter was well made. That way you can try/use a variety of digital rca terminated cables.
The big advantage of BNC is the rock solid impedance. When you use the adaptor you lose that. Impedance mismatch is the greatest source of jitter in digital audio transmission
Alan
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.
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.
I'm not sure if this helps, as it was between a cd player used as a transport with digital out to a DAC.
The Good: The BNC output to the RCA input sounded best versus the RCA to RCA input.
The Bad: Though the digital out had options of RCA or BNC, the digital input only had RCA option. So no way to experiment.
The Ugly: Defied logic. 3 cables, an RG 59U 75 ohm, DH 75 Silver Sonic Digital, a VH Pulsar Digital were all tried. Then a 4th cable bested them all, and it was a old QED interconnect not even meant for digital. Who knows why? All cables were per recommended lengths for digital cables.
In summary, repeating myself, I guess my experience showed that BNC at the output going to RCA was better than RCA to RCA.
Hope that helps a bit?
Cheers!
Ed
"I know just enough to get into trouble. But not enough to get out of it."
Not sure what you asking.
S/PDIF (Sony/Philips Digital Interface Format) is a type of digital audio interconnect used in consumer audio equipment to output audio over reasonably short distances. The signal is transmitted over either a coaxial cable with RCA connectors or a fibre optic cable with TOSLINK connectors. S/PDIF interconnects components in home theatres and other digital high fidelity systems.
S/PDIF is based on the professional AES3 interconnect standard.[1] S/PDIF can carry two channels of uncompressed PCM audio or compressed 5.1/7.1 surround sound (such as DTS audio codec); it cannot support lossless formats (such as Dolby TrueHD and DTS-HD Master Audio) which require greater bandwidth like that available with HDMI or DisplayPort.
S/PDIF is a data link layer protocol and a set of physical layer specifications for carrying digital audio signals between devices and components over either optical or electrical cable. The name stands for Sony/Philips Digital Interconnect Format but is also known as Sony/Philips Digital Interface. Sony and Philips were the primary designers of S/PDIF. S/PDIF is standardised in IEC 60958 as IEC 60958 type II (IEC 958 before 1998).[2]
https://en.wikipedia.org/wiki/S/PDIF
See the Link below for BNC connectors for Belden 1694a coax cable.
Quality? Unknown.
For what it's worth a BNC connector is a true 75 ohm connector.
Most, if not all, digital audio equipment today use RCA jacks.
Bnc can be and is in my setup using SPDIF. One is a protocol and the other a termination. What I have used is just a coax cable terminated in BNC connectors. Of course the device you are connecting have to have BNC ions
I like I2S better using an Eithernet cable
Alan
Edits: 01/24/16
I am looking at the Belden 1694A for the SPDIF connector.
The outer diameter of Belden 1694A coaxial cable is 6.93mm. Other than choosing a connector that will accommodate the particular cable, what do you specifically need to know about the topic?
1694A is a cable not a connector. I've never seen a SPDIF that wasn't an RCA.As a rule the BNC will be the more picky in terms of needing a certain cable size. Do you plan on using a crimp type BNC?
ET
Yes I understand. My mistake. The actual RCA connector on the is a Canare CANRCAPC53.
So... my plan is to put a BNC connector on one end.
I'm thinking this would be superior to a BNC adapter.
But as always and as others indicate, experimentation will be in order.
As I said above BNC on one end and rca on the other screws up impedance. More jitter. However doesn't mean you won't like the results
Alan
I'm not sure what i can do about that. I have a devise that outputs in BNC and a DAC that has and SPDIF input.
I asked the DAC manufacturer about changing the RCA/SPDIF input to a BNC and he scoffed and told me to just use an adapter.
So, I'm thinking the BNC on one end an a RCA on the other is better than using an adapter... but like I said, not sure where to go next.
Blue Jeans Cable sells Belden 1694A digital coaxial cable terminated with BNC, RCA, or both.
You can even choose which end you want the BNC and RCA to be terminated based on the directional flow of the particular cable.
See pull-down menus for selecting various options to choose from.
See link:
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