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In Reply to: RE: Here's my calculation, which is based on the word-clock rate (but I assumed 16 bits) posted by John Marks on April 21, 2016 at 18:06:12
S/PDIF transmits data serially in 32-bit subframes, each containing one audio sample. So for 24/96 PCM, the bit rate is 2 channels * 32 bits/sample * 96000 samples per second = 6.144 MHz (that was the spec for the original standard). S/PDIF uses bi-phase encoding, so the clock frequency is twice the bit rate = 12.288 MHz. And the width of one pulse on the wire is one half of a clock period = 4.069e-8s. If you assume your propagation velocity is 0.75c, which is relatively high (PTFE is around 0.7), then the length of a pulse on the cable is 9.15 meters. For 44.1 PCM, it would be 19.9 meters. Not 3 miles, but still a fair bit bigger than 3.5 inches.
Anyway, it's the transitions that matter, not the length of time between transitions.
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BTW, in a private email, John Atkinson quoted different numbers, and again in a private email, Charley Hansen quoted different numbers.
I have always said that my cable design is what it is, it sounds as it sounds, and whether it sounds good is despite my efforts rather than because of them doesn't matter if the customer is happy.
(I know competent engineers who claim that any properly working DAC can cope with minute timing errors and therefore cables cannot matter... .)
I have never claimed that my cable is "best." I think digital cables are rather system-specific. I think that my cable is a valid option and I am happy with its sound, at the price. I could (in theory) make a hugely expensive cable but at this point I have no idea whether it would sound better.
Anyway, it's "Countdown-to-Campari Time" here at Esperanto Audio's worldwide headquarters' executive suites.
Tee hee.
John
Pretty sure I was off by a factor of two because I didn't need to double the clock rate.
Anyway, if we knew the bandwidth of a typical transceiver driving the cable, we could estimate the rise & fall times on the transitions. Or you could just measure them with a scope. It wouldn't surprise me if the length of a transition is on the order of the length of the cable, meaning the cable isn't easily characterized by either transmission line or lumped impedance models.
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