Also to ad to Al's comments, make sure it's proper 75ohm cable as many are 100ohm, and yes the bnc connection is a 75ohm, where rca are not.
Cheers George
COAX Cable length 1.5 meters
There are many threads and articles suggesting the optimal length for a digital coax cable to be 1.5 meters (or a very short length). Now, what I am submitting to the those in the know, couldn't that length change depending on the materials used to manufacture the cable? Let's assume the cable has BNC connectors and measures exactly 75 ohms.
Belden coax w/ BNC uses a copper conductor and a tinned copper braid and a double-sided aluminum-on-polyester foil shielding. Recommended length by users is 1.5 meters.
The cable I am interested in comes terminated as 1.3 meters. It is OYAIDE from Japan.
http://www.oyaide.com/ENGLISH/AUDIO/products_category/digital_cable/pg532.html
The conductor is pure silver, with a Teflon dielectric and Foamed Polyethylene insulation. Shield is Copper foil + Silver plating copper. So, I ask you, wouldn't the materials influence the timing of the signal and thus the optimal length?
Belden coax w/ BNC uses a copper conductor and a tinned copper braid and a double-sided aluminum-on-polyester foil shielding. Recommended length by users is 1.5 meters.
The cable I am interested in comes terminated as 1.3 meters. It is OYAIDE from Japan.
http://www.oyaide.com/ENGLISH/AUDIO/products_category/digital_cable/pg532.html
The conductor is pure silver, with a Teflon dielectric and Foamed Polyethylene insulation. Shield is Copper foil + Silver plating copper. So, I ask you, wouldn't the materials influence the timing of the signal and thus the optimal length?
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Very nicely explained, Al. Thank you. In the case of the cable I have been reading about, it seems as though the manufacturer in Japan decided on a 1.3m length when it was added to their product line. All of which is why I have said in a number of past threads that the recommendation of 1.5 meters (or a bit longer)Yes, I’ve seen your post before. After reading about the Japanese cable in question, the many positive user reviews, and their willingness to publish specs, perhaps they have found their cable performs best at this length. It is the only length available for BNC. The variable in the tests would be the DACs and power supplies being used. |
Hi Lowrider, Yes, the "dielectric constant" of the insulating material(s) surrounding the conductors in a cable, and particularly the constant of the dielectric material that is between the inner and outer conductors in the case of a coaxial cable, will affect the speed with which the signal propagates through the cable. For various types of coaxial cable that velocity may range, roughly speaking, from perhaps 60% to 90% or so of the speed of light in a vacuum. And that variation can affect the lengths that will be optimal in a given application. As can many other variables, including the almost always unspecified risetime and falltime of the signal provided by the particular component which drives the cable (risetime and falltime refer to the time it takes for the digital signal to transition between its two voltage states), the impedance accuracy of the two connected components as well as of the cable, the jitter rejection capability of the DAC or other component receiving the signal, the susceptibility of the two components to ground loop issues (which can also be affected by how AC power is distributed to them), and other unpredictable, system-dependent, and probably also listener-dependent variables. All of which is why I have said in a number of past threads that the recommendation of 1.5 meters (or a bit longer), or alternatively a very short length, should be viewed as providing the best odds of being optimal, but one that will not necessarily be optimal in many cases. Best regards, -- Al |
