I finally found some time to make some USB and S/PDIF cable measurements. These are using my 6GHz Scope with jitter software. The scope input is terminated with 75 ohms. No probe used. The histograms show the variation of cycle-time over thousands of samples. These were all made using the Off-Ramp 5 driven from PC laptop running XP and Foobar. Not the best, but okay for comparisons. The test file was music in .wav format at 96kHz.
The first set are S/PDIF cables.
Starting with the 1.5m Bitmeister S/PDIF cable ($650) that I used to manufacture. 75 ohm BNC to RCA adapters at both ends:
Next, my new BNC-BNC 4 foot cable that sells for $250:
Quite a bit better than the older more expensive cable.
Now for some USB cable measurements. Note the change in axis time. 41 psec per division. This is automatically selected by the software.
First a 5m Belkin Gold:
Next a 5m Polestar:
This has less "lumpiness" and "bulges" in the base of the distribution. The spires are less separated.
It should have a smooth ramp up and down and very steep spires. A single spire would be best, but not critical. This indicates some assymmetry in the rise and fall times.