Measuring Digital Cables - JPS Labs Superconductor 2

House de Kris

Loud-n-Deep
Another digital audio interconnect as supplied by AKer DKak. This time the cable under consideration is the JPS Labs Superconductor 2. This is a 0.75m fat-n-rigid cable terminted in gold BNCs. This fatty has a cloth covering and feels very nice in the hand. It has a couple of inches of heat shrink tubing at the terminations with the company and product name printed in gold. When I say rigid, I mean this thing wants to hold its shape no matter what. Really, this thing is rigid is the point I'm trying to make. It is so rigid, I had difficulty connecting it to the TDR since its two jacks are only about 2-3" apart. Printed on the heat shrink tubing were directional arrows, and I respected them for these measurements.

The TDR measures the impedance of this cable as being 49.97ohms. Yes, this is a 50ohm cable. The story continues. Although the gold BNCs look like 75ohm connectors (which I believe they are), the TDR shows an impedance dip at each end of the cable. I think this cable has similar issues to the PS Audio Digital X Stream cable, in that attaching a fat cable to a smallish connector requires stunts that compromise the controlled impedance nature of a transmission line. I believe fat cables like this are better suited to fat connectors, like N-type.

The network analyzer measured the -3dB bandwidth point as being 4.6GHz.
 

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Very interesting. Makes me wonder how much of the "specialness" attributed to some digital cables is the result of impedance match/mismatch, and the degree to which certain equipment is sensitive to that.
 
What you say, RichPA, may be entirely true. From what DKak has indicated, some of the cables that measure closest to the ideal transmission path are some of the cheapest cables. Like the Belden 1694A or Canare L-5CFB with simple crimp connectors. I guess it is similar to some of the exotic speaker cables out there that put excessive reactive components on the output of an amp to get a different sound.

Finding that this was a 50ohm cable was quite a surprise. I checked and verified a few times to ensure I wasn't fooling myself. It could be that this was an honest mistake on the part of JPS Labs. Or, it could have been built exactly as JPS desired, I sure don't know. I just spend a few moments at the JPS website. Seems Superconductor 2 is now discontinued replaced by, you guessed it, Superconductor 3. I could find no claim for characteristic impedance on any page referencing the Superconductor 2.
 
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