We were told only use 75 ohm cable for SPDIF purpose. So what is the impedance of typical analog RCA audio cable?Another question is I have a 75 ohm TV antenna cable, is it suitable for SPDIF purpose?Some people said that wrong impedance may not cause problem if the cable is short enough, if it is true, then what cable length will cause problem?I ask these because I just made a SPDIF cable with two spare RCA plugs and a 75 ohm TV antenna cable (3 feet), I tested it using RMAA and found no problem (+- 0dB freq. response, -146dB noise level, 0% THD and so on) and I can't hear any problem as well. Does it mean that I don't need to spend money to buy a standard cable?Thanks.
I have references for & [c]
d] RG-6QS (Quad Shield) is designed for the very high frequencies of cable TV so it's not the best choice for digital or analog audio. Ordinary RG-6 is a better choice.
F-pin and BNC connectors would technically be the proper termination to maintain the 75 Ohm rating that S/PDIF is looking for
I think my cable is RG-6 after a photo search.
Quote from: Speedskater on 25 November, 2012, 11:41:26 AMI have references for & [c]I'd be interested in a reference for [d].
I think that what is being referred to is the fact that most quad-shield RG-6 has what is known as a copperweld center conductor. This means that the wire is copper over steel (for strength)
I've found SPDIF rather resilient when run over cables that are not to spec. I've got a 30' run that is made of a standard 1/8" phono jack extension cable (because it's what I had) with adapters on either end. The far end has a splitter to feed it into an old set of cambridge soundworks 4.1 speakers that needs separate inputs for the front and back pairs. A very hackish solution and definitely not in spec, but it works fine.
Are you sure your speakers aren't being fed by a TTL signal?
RG6 and RG59 look the same in photos, but RG6 is slightly larger and stiffer, which makes it harder to work with in a tight stereo cabinet. If the center core wire diameter is around 1.02 mm, then you have RG6, if it is .64 mm then you have RG59. Both should work well but be careful not to bend them too tightly; in best practice never more than 6 inch diameter circles should ever be attempted. Many people understand the danger of snapping the inner core, but what a lot of people don't realize is you also potentially can compromise the performance of the wire if it is bent more tightly than this, even if you don't snap or kink the center core.
Both exist:A general point is that, up to 10MHz, it doesn't really matter. On short runs, it doesn't really matter.RCA/phono connectors were never designed to work at 6MHz, and often exactly the same cable is used for audio and video connected to phono connectors. On short runs, it's usually good enough for SD analogue composite video, and more than good enough for SPDIF digital audio. Cables designed to work with analogue HD video (or shall I say, cables that work really well with analogue HD video) are probably some of the best consumer cables out there. If they make great HD video cables, they'll make exceptional SPDIF cables. Though they normally come in triplets!(I'm not claiming any audible difference from using better cables for SPDIF. I doubt there any detectable differences even in the SPDIF raw signal over short runs, never mind the audio that's decoded from it. On longer runs, you might reach a point where differences became detectable.)Cheers,David.
Quote from: Arnold B. Krueger on 25 November, 2012, 08:53:11 PMI think that what is being referred to is the fact that most quad-shield RG-6 has what is known as a copperweld center conductor. This means that the wire is copper over steel (for strength)This is done for economic reasons only.
I have in front of me copperweld RG6 and RG6QS. I also have solid copper RG6 and RG6QS. So if you mean "most inexpensive cable" instead of "most" I'll agree, but I still want to see any evidence than the preponderance of RG6QS being copper-over-steel is higher than that of RG6.
I constantly notice repetitive difference even in audiophile grade coaxial cables. My undisputed winner is [removed] coaxial cable....
...much thicker and deeper sound