On January 6, 2018 at 14:26, Ernie Gilman said...
How does this relate to the original question? Well, that RCA cable was perfectly capable of carrying 10.7 MHz ! That is WAY WAY WAY above the audio spectrum. The keys are -- good connectors, excellent soldering (the shield was soldered to the connector's ground all the way around the connector), but most importantly, the entire cable assembly was only about five inches long.
Ernie, the data transmission of S/PDIf over coax is not running at analog audio frequency. Because it is a serial stream and has to carry both channels, and clock, the transmission frequency of S/PDIF is 128 times the sampling rate. So for typical 48 KHz sampling that is common for video soundtracks, the data rate is 6.144 Mhz. That is a heck of a lot above the 24 Khz maximum audio bandwidth we can create with 48 Khz sampling.
In addition, the process of extracting clocks looks at zero crossing point of the waveform. The lower the bandwidth of the cable, the slower that transition and the more possibility for jitter.
So ideally you would want to have a pretty high-bandwidth cable for S/PDIF.
That said, for short lengths it doesn't matter as mentioned. :)
