Regarding length on digital cables S/PDIF
Bryston newsletters: > > http://www.bryston.com/newsletters/52_files/vol5is2.html > > What about DIGITAL AUDIO CABLES? > [...] > This requires that sufficient numbers of related harmonics associated > with the fundamental are transmitted distortion free to minimize > jitter. To achieve this, it is desirable to transmit without distortion > frequency components as high as 50 times the fundamental frequency. This > places the range of wavelengths of the data stream between about 58 > metres and 1.2 metres. Once again, this is not a time to get sloppy > with your choice of cables or impedance matching. Check the source and > load impedances of your digital equipment and make sure your select > cables with the appropriate characteristic impedance, > [...] > > > http://www.bryston.com/newsletters/53_files/vol5is3.html > > DIGITAL CABLES > With 'Digital' interconnects things are a lot different. The > wavelengths of digital signals are 'very short' (same for FM) so the > lengths and terminations are much more critical than with the analogue > signals previously discussed. When the wavelength of the signal the > cable is used for approaches 1/30th of the length of the cable then > transmission line effects start to appear and much more attention has > to be paid to the connection and termination. If not then reflections > and cancellation of data is a real possibility. For instance the > AES/EBU digital connection on the back of the Bryston SP1 should be > used with a cable having an impedance of 110 ohms. > See also:'PFO Audio Discourse: Why longer is generally better for an S/PDIF Digital Cable' (http://www.positive-feedback.com/Issue14/spdif.htm) av Steve Nugent ('Empirical Audio' (http://www.empiricalaudio.com)) i Positive Feedback Online - Issue 14. > > [...] > Many of you may have heard or read that it is beneficial to use at > least a 1.5m length digital cable from your Transport to your DAC. > There are actually technical reasons for this, > [...] > If the rise-time is 25 nanoseconds and the cable length is 3 feet, then > the propagation time is about 6 nanoseconds. Once the transition has > arrived at the receiver, the reflection propagates back to the driver > (6 nanoseconds) and then the driver reflects this back to the receiver > (6 nanoseconds) = 12 nanoseconds. So, as seen at the receiver, 12 > nanoseconds after the 25 nanosecond transition started, we have a > reflection superimposing on the transition. This is right about the > time that the receiver will try to sample the transition, right around > 0 volts DC. Not good. Now if the cable had been 1.5 meters, the > reflection would have arrived 18 nanoseconds after the 25 nanosecond > transition started at the receiver. This is much better because the > receiver has likely already sampled the transition by this time. > [...] > Me? 6 feet BJC and 3 feet BJC. Using the 6 feet of course ;) -- NoRoDa ------------------------------------------------------------------------ NoRoDa's Profile: http://forums.slimdevices.com/member.php?userid=49139 View this thread: http://forums.slimdevices.com/showthread.php?t=91322 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/mailman/listinfo/audiophiles
