I would like to add the following in the discussion: Remember, I'm an electronics engineer so this gets a bit technical;
Transmitting a digital signal over fiber optic cable has several advantages over transmitting the same signal over copper. They are: 1. complete electrical isolation (ground loops don't exist) 2. complete immunity for EM interference (no transformer hums can creep into the cable, no need for shielding, surge-protectors etc.) 3. with several options available for the light-source, from low-power IR LED to high power laser, length of cabling is much less of an issue as compared to copper. 4. very high capacity. When I left this "scene" in 2002, we could do 2.4 Gbps through a single fiber... -per color-. (Using different colors of light-sources mixed into a single fiber (like red, blue, green lasers) you can get 2.4 Gbps per color). Digital audio at 44/16 uses a fraction of this capacity, let's keep it at a couple of percent meaning we don't have high-end requirements for cable quality.... any piece of honest optic cable should be well within our requirements for digital audio even at much higher sample-rates and bit-depths.. So, all of the above is nice. Now we get to distortion of the signal while it travels down the cable. Any distortion you get here is not really bad as long as you are able to detect it correctly at the receiving end. When the signal at the receiving end (after detection and back in electrical form) is exactly the same as it was before it was converted to light-form at the transmitting end, any distortion while in the light-form is irrelevant. Timing should not be an issue anymore since they started encoding the timing into the digital signal... (correct me if I'm wrong there). The good thing about this all is that the quality of the complete chain can be measured with equipment because it's all in the digital domain. If you measure it to be exactly the same, no change in sound can be detected, period.... but .... that's all optical and not a comparison with coax yet, I'll come to that later but let me finish my conclusion on optical first: The optical properties of plastic are worse than for glass. So, one is able to make a better cable from glass as compared to plastic. One is also able to make a really bad cable out of glass which would be inferior to a good plastic cable so there you go. However, even a not-so-good cable might end up with perfect results as there is some room for degradation of the signal while still ending up with bit-exact results like I described above. IMHO, the connectors used for the fiber-optic cable and/or the chassis-parts are much more important than the cable itself.... the male-female parts should be the same brand and type. When the 2 pieces of equipment have different brands of connectors it would be good to have a cable with the same two brands of connectors so they match at both ends. Anyone who can splice fiber (and there's many many than can today) can make such a cable in minutes. connectors and splices are the weak-link (sic?) I think. Now, you have the best optical and coax cables and you try them both in listening tests.... and they sound different. Interesting to say the least! My first reaction is that the two setup's differ in more ways than obvious. With coax, we do -not- have that electrical isolation for starters. The first thing to try would be to test for any difference between the optical link without the coax present and optical with the coax present even though it's doing "nothing". "Nothing" is between quotes because even though you're not using it in the transmission-path, it is creating two electrical connections and specially the ground connection can make a difference... even more so when the receiving end of the cable is the DAC with it's analog circuitry. You never know... maybe you prefer that nice warm hum from a ground-loop ;-) When both cables are good and a difference in sound is noted... I tend to think that the change occurred indirectly (like a ground connection) in the analog domain. cheers, Nick. -- DeVerm ------------------------------------------------------------------------ DeVerm's Profile: http://forums.slimdevices.com/member.php?userid=18104 View this thread: http://forums.slimdevices.com/showthread.php?t=52817 _______________________________________________ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
