Originally they were. Lately I have toslink cables also referred to as synonymous with S/PDIF, but that isn’t the way it used to be...
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S/PDIF refers to the signalling, not the conductor type. Coaxial and TOSlink are both using S/PDIF https://en.wikipedia.org/wiki/S/PDIF Fiber has the advantage of never causing a ground loop, which can have odd effects in digital, which may or may not be audible as a traditional ground loop. Some swear that copper sounds better, which could have something to do with the connector hardware/drivers. I've long ago switched to USB. |
jss49 - The problem with your suggestion is that doing a google search on any subject, audio or otherwise, brings up at least as much bad or confusing information as good. I think it's perfectly reasonable for someone to ask basic questions here where there's a least a somewhat higher probability of getting a useful answer. Fortunately there are quite a few experienced folks here who don't seem to mind helping a newcomer. |
There are many types of coaxial cable. SPDIF cables are typically made of coaxial cable ("coax") with a 75-ohm characteristic impedance. Regarding bandwidth, the SPDIF specs and those of the receiving and sending units are more likely to limit bandwidth than the actual cable used. What lies beyond 192? Opinions vary widely. Mine is that beyond 24/96, there is little or nothing added other than marketing fluff. |
I used a spare RCA interconnect (nominally 50Ω) for Spdif when I first got a DAC, it worked but a cable designed for the job but with RCAs on both ends was quite an improvement and a 75Ω cable with BNC connectors (Belden 4794R) better still even though it was designed for 12G SDI video and I had to use an adaptor at the DAC end because Rega didn’t see fit to put a BNC socket to their DAC. I think they were all coax cables. |
crusty and yeti have it right clwinbe hasn’t a clue here is a tutorial to help educate https://darko.audio/2018/11/why-isnt-digital-audio-just-ones-and-zeroes/ |
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To answer your question, S/PDIF is a specific digital communication protocol to encode and transfer 2-channel PCM music data as well as multi-channel Dolby Digital and DTS data. Technically speaking, any wire can be used to connect an S/PDIF source to a S/PDIF target/receiver. However, COAX cables are mostly recommended because of their shielding (which is critical on a S/PDIF cable) and the ability to try to adhere to the 75 ohm requirement for S/PDIF transmitter/receiver specification. In reality, only COAX cables properly terminated with a 75 ohm BNC connector will match this criteria. Cables that are terminated with RCA generally have a lower impedance (I think it was somewhere around 24 ohms or so). There are a couple of other mechanisms that have been created to transfer this same S/PDIF data: toslink - a glass/fiber cable which uses light pulses to transmit the S/PDIF data instead of electrical pulses. Like others have said, it electrically disconnects the source/target so that there is no ground loop hum transmitted. The downside is that it's not a perfect transfer medium because the LEDs (light emitting diodes) just cannot light up fast enough to create a perfect square wave. The result is almost a curvy sine wave. Sound quality is not going to be as good as a high quality COAX. AES/EBU - uses an XLR cable that should be engineered to have 110 ohm impedance. The digital pulses are exactly the same as digital COAX, except they are balanced. One conductor of the XLR transmits a positive square wave, and the other conductor transmits a negative square wave. Generally, both of these conductors are connected to the primary wires of a small transformer on the target/receiver (one conductor pushes voltage while the other conductor pulls voltage). Theoretically speaking, you could take the positive conductor and just connect it into a standard digital COAX input (because the signal is exactly the same). |
The above is a very thoughtful and informative answer. Is a coaxial cable same as a SPDIF cable? Seems they are one in the same.The simple answer in home audio applications is yes. Coax with a BNC termination will conform to the 75ohm S/PDIF standard. I have been told by a cable designer (Rick Schultz) that RCA digital coax can come close to 75ohms depending on the design. http://www.bluejeanscable.com/articles/75ohmrca.htm |
AES/EBU - uses an XLR cable that should be engineered to have 110 ohm impedance.Like with S/Pdif, AES/EBU is an audio transfer standard and not the cable. It can be used with 110 ohm XLR cable (IEC 60958 type I), with 75ohm coax or Toslink (IEC 60958 type II). XLR is just most common cable with AES/EBU. The main difference between S/Pdif and AES/EBU standards is in the property rights. S/Pdif includes Serial Copy Management System, preventing second-generation copy in some instances. Most of AES/EBU used in consumer audio is S/Pdif standard. It is assumed to be 110 ohm XLR only because that was the most common use of AES/EBU (studios). Also, AES/EBU was defined as 24 bits while S/Pdif was 20 bits + 4 auxuliary bits, but these 4 bits are used (almost always) as data extension to make total of 24 bits. So, in consumer audio both "AES/EBU" and "S/Pdif" follow S/Pdif standard and name difference is customary for different cables and electrical levels. |
If the AES3 XLR cable can be connected to RCA with a simple adapter it is SPDIF which is really now considered a variant of AES3 if you need an impedance converter for it to work it is AES3 type 1 or the old AES/EBU standard. AES3 is used in professional installations with XLR 110 Ohm balanced or BNC 75 Ohm unbalanced. |
if you are running optical spdif the key, an absolute key, is to get a true glass fiber (not plastic) cable - with this, the sq gap is equalized to electrical spdif there are some reasonably priced ones out there, just search but know that alot of the ’audiophile’ toslink cables marketed out there as such are still plastic conductor... |
Digital Coaxial is considered the better way to go, at least from all I’ve read. So that is what I use. However, to be honest, I’ve used toslink or photo optic cable prior and can’t say I notice an apreciable difference in sound quality. Same thing with the silver cables (silver plated) VS copper speaker cable debate.... they both sound good to me. I like my Qed silver anniversaries....however, when I can afford them, I will grab a pair of auditorium 23’s.... |
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Does SPDIF just take the I2S format and just change into a single connection instead of 5 connections.No, they are two different formats. The main difference is that I2S contains both data and the clock (separate wires), while with S/Pdif you have to extract clock from the data stream (one wire). Yes, you can have multiple devices on I2S bus, but the main reason for it in audio is to have better (less jittery) control of the clock. |
No, they are two different formats. The main difference is that I2S contains both data and the clock (separate wires), while with S/Pdif you have to extract clock from the data stream (one wire). Yes, you can have multiple devices on I2S bus, but the main reason for it in audio is to have better (less jittery) control of the clock. I thought I2S was used internally in a piece of audio equipment, and S/PDIF was used to transmit it to another piece of audio equipment. Seems like Sony and philips would have used a better format than s/PDIF. |
