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Optical to rca cable10/2/2023 ![]() ![]() ![]() The amount of jitter in the recovered clock depends on how much jitter is in the incoming signal transitions, and the ability of the PLL to reject it. This is done with a PLL synchronized with the incoming SPDIF transitions. SPDIF embeds the clock into the signal, so it must be recovered. This is a "receiver not doing its job" problem, not a cable problem. If the receiver doesn't clean jitter properly then you'll have audible differences between cables. If it does it properly, there will be no measurable difference, and good luck hearing anything in a double blind test. This only matters if your DAC at the receiving end doesn't implement proper clock recovery (ie, WM8805, ESS DACs, or other FIFO-based systems). If the coax implementation is botched (not enough bandwidth extension on the low end, violation of 75R impedance, high intersymbol interference, etc) it can also add jitter. Optical receivers add a lot more jitter (in the ns range) than well-implemented coaxial. Also SPDIF includes error-checking, so the receiver will mask any errors. Anyone who talks about bit errors in SPDIF has something to sell, usually an expensive gimmick to solve a non-existent problem. If the digital signal is too attenuated the receiver won't be able to decode it, or errors will occur).īarring a major issue, all the bits will be there with both systems (I checked). (Note 1dB/m is for the digital signal, not the analog audio. Connectors are, of course, not compatible. This isn't high-quality glass-core telecom fiber with 1-2dB/km loss! This doesn't matter for a 1m long fiber in your home cinema, but if you need a 100 meter run, coax will be the only option. Whether 192k is a marketing gimmick or useful is an interesting question, but if you want to use it and your optical reveiver doesn't support it then you'll have to use coax. Of course you can buy optical transceivers with much higher bandwidth (for ethernet, among other things), but you won't find these in audio gear.Ĭoax has no trouble with bandwidth, it'll pass 384k with no trouble, whether it will sound better is left as an exercise for the marketing department. That's rather binary: it works or it does't. ![]() If you want to know which one you got, make a test. The majority of optical transceivers on the market will have enough bandwidth for 24bits/96kHz, but only a few will pass 24/192k, and none pass 384k. This really matters for cable TV boxes which are connected to the cable's ground, as this tends to create annoying ground loops. A quick test with a multimeter between digital RCA ground and any other RCA ground will reveal if there is transformer isolation or not. Coax can also be isolated with a transformer, however this adds to the cost and is uncommon in consumer equipment. Optical fiber isn't conductive, so it solves ground loops, hum/buzz issues and any is insensitive to RF interference. I want to ask, within the scope of digital audio transmission, it is their any observable or measurable differences between the two cables? Needless to say, this issue is not present in the optical versions, and thus they are more suited to hot-plugging. For this reason I have often been told that you should always connect the RCA connectors first, before connecting the entire system to the mains voltage - or use the ground lug that some of these devices have to reference the system to mains earth at all times. In the RCA connectors, the first connection is the center pin that carries the data. If data is connected first, this still happens - but the currents to do so now have to flow through your likely far more sensitive digital receiver circuits. As a result, the two circuits being connected are first pulled to the same potential, and then the actual data is connected. If you look at most modern connectors, you will see that the ground connection is made first. It also means that the grounds can't act as a big antenna which might make it easier to get low noise in the system as a whole.Īnd additional disadvantage of the RCA connectors is in the ground connection. As a result, there might be less issues with ground loops, networks can remain isolated, etc. In the case of optical, there is galvanic isolation between the two. With RCA, the two networks connected have to be referenced to each other. In addition to the answer of TimB, there is another advantage of this optical communication.
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