Short coax digital cable: qed audioquest ricabl

Some years back, I owned a California Audio Labs Delta CD transport and their Alpha DAC. I bought a .5 Meter Kimber Orchid, as the Orchid was supposed to be an excellent AES/EBU cable. It was terrible(the crappy Monster coax I tried first, sounded better). I replaced it with a 1.5 Meter Orchid and found bliss. Just my lesson learned about digital reflections and cable lengths. If I ever happen to again need an AES/EBU cable, I'll be shopping for an Orchid.

Rodman, It is system thing, as Al stated, but in your case it is possible that your transport had about 10ns transition time. Beginning of the transition resulted in reflection from the end of the cable (impedance boundary) coming 5ns later (5ns/m x 0.5m x 2) deforming shape of original transition in the middle, affecting threshold crossing time (jitter). With 1.5m cable first reflection came back 15ns later completely missing transition. Of course it is only a speculation. In addition propagation time is dielectric dependent. (assumed 5ns/m comes from 60% of light speed). Best thing is to try what works best.

Hi Jim,

A notable statement by the person with whom you were debating was:

Are they aware that the S/PDIF interface has a defined jitter margin? If I am remembering correctly, it is +/- 20 nanoseconds for 1 Fs (44.1 kHz/48 kHz) transmission, which is what the vast majority send over S/PDIF interfaces.

I would refer him to the following paper, co-authored by Professor Malcolm Hawksford, a distinguished British professor/academician/researcher/PhD/DSc/Fellow of the AES (Audio Engineering Society)/AES Silver Medal honoree "for major contributions to engineering research in the advancement of audio reproduction":

Is The AES EBU / SPDIF Digital Audio Interface Flawed?

An excerpt from its conclusion:

A simple model of jitter error audibility has shown that white jitter noise of up to 180 ps can be tolerated in a DAC, but that even lower levels of sinusoidal jitter may be audible. These limits place tough constraints upon digital interface design....

180 ps is less than 1% of the 20 ns figure cited by the person you were debating. Also, Professor Hawksford’s paper was presented to the AES in 1992; presumably the increased resolution provided by many of today’s systems makes low level jitter even more of a concern than it may have been in 1992.

Best regards,
-- Al