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Post by DavidR on Aug 25, 2022 12:08:40 GMT -5
I'm in the need for some RCA cables for an analog signal. Typical (standard) RCA wires with 22AWG (stranded OFC), gold plated pins, shielding, etc or RCA cables with RG-6/U wire ?
I'm under the impression that the RG-6/U wire is for a digital signal. The shielding looks better but not by a lot.
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Post by AudioHTIT on Aug 25, 2022 12:41:43 GMT -5
So you want to buy new cables and are looking for recommendations? Or you want to buy used here? What length? Some cable, like that found in BlueJeans component video cable, also works well for analog and digital audio. Somewhere on the BJC site he talks about this. I used some 6 foot component cables for a pair of analog RCA runs, worked great, nice connectors too!
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Post by DavidR on Aug 25, 2022 12:49:17 GMT -5
Buying new cables. I was unsure on the single wire RG-6/U that basically looks like coaxial cable for an analog signal.
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Post by AudioHTIT on Aug 25, 2022 13:15:55 GMT -5
Buying new cables. I was unsure on the single wire RG-6/U that basically looks like coaxial cable for an analog signal. Here’s the article I was talking about, but don’t know if he goes into solid core vs stranded, I’ve preferred stranded for flexibility, but not sure about performance. www.bluejeanscable.com/articles/digitalanalog.htm |
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Post by 405x5 on Aug 25, 2022 13:17:21 GMT -5
Buying new cables. I was unsure on the single wire RG-6/U that basically looks like coaxial cable for an analog signal. Just buy your cables specific to the application (RCA, etc.) and length necessary to complete the mission. A good quality audio cable may internally be similar to RU6, RG59 or 58, but nobody buys it like that. |
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Post by DavidR on Aug 25, 2022 13:27:32 GMT -5
Buying new cables. I was unsure on the single wire RG-6/U that basically looks like coaxial cable for an analog signal. Here’s the article I was talking about, but don’t know if he goes into solid core vs stranded, I’ve preferred stranded for flexibility, but not sure about performance. www.bluejeanscable.com/articles/digitalanalog.htmThanks for the link.
Upon closer look the 22AWG RCA cables also use coaxial cable (RG-59 75 ohm coaxial). I too prefer stranded wire. |
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Post by 405x5 on Aug 25, 2022 14:17:06 GMT -5
Thanks for the link.
Upon closer look the 22AWG RCA cables also use coaxial cable (RG-59 75 ohm coaxial). I too prefer stranded wire. I don’t think in all my years of “hooking things up”, I’ve ever owned or used an RCA interconnect that was anything but stranded. I do have a few of the “cute” ones with those ARROWS that point you in the right direction. |
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Post by DavidR on Aug 25, 2022 14:38:43 GMT -5
IIRC the ones with the arrows means the shielding is only grounded at one end.
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Post by creimes on Aug 25, 2022 14:43:08 GMT -5
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KeithL
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Post by KeithL on Aug 25, 2022 15:52:00 GMT -5
I have a suspicion that most people don't actually understand what "the impedance of a cable" actually means.
The easiest way to explain this in non-technical terms is to use an example.
Let's start by connecting a signal source directly to "a pure 75 Ohm resistor".
When we do so our source will "see" a load of 75 Ohms at all frequencies (at least over a very wide range of frequencies).
Now let's put a long coaxial cable between the signal source and the load.
Because that cable has both inductance and capacitance, which become part of the load, the source will no longer see a pure simple resistive load.
In most cases, at some frequencies the capacitance will dominate, and at other frequencies the inductance will dominate, so it will no longer look like "just a resistor".
And, if our source is delivering a signal that is a mix of a wide range of frequencies, this will tend to garble the signal in various ways.
A "75 Ohm cable" is a cable that has been chosen such that its capacitance and inductance "balance out at a characteristic impedance of 75 Ohms".
In simplest terms this means that, if I connect THIS cable to our source, and put a 75 Ohm resistor at the other end, my source will "see" a pure 75 Ohm resistor as its load.
When this happens we say that "we have used a cable with a characteristic impedance of 75 Ohms and terminated it with a 75 Ohm load".
And, when I do this properly, if our source is delivering a signal that is a mix of a wide range of frequencies, that signal will NOT be garbled.
This is what we're doing when we "use the proper digital cable, with the proper impedance, so that we can get a clean square wave to the other end".
The important thing to note is that this is a significant issue at VERY high frequencies... and less important at lower frequencies.
It is VERY important at the frequencies used by broadcast television (which is why you use "75 Ohm coax" or "300 Ohm twin lead" with an antenna).
(If you fail to do this correctly you may well end up with a signal that is so weak and garbled that it is unusable.)
And, even at the frequencies used by "video" signals it can be significant.
BUT IT IS *NOT* SIGNIFICANT AT AUDIO SIGNALS OVER THE LENGTHS INVOLVED WITH AUDIO INTERCONNECTS.
The bottom line of all this is this:
Home VIDEO gear is generally designed to operate specifically with coaxial cables with a characteristic impedance of 75 Ohms.
So, if you try to use an AUDIO interconnect to carry a video signal, it may or may not work well.
(This is because, since the impedance doesn't matter much for audio signals, an audio interconnect may or may not have a characteristic impedance of 75 Ohms.)
HOWEVER, as it turns out, audio interconnects with a rather wide range of characteristic impedances will all work well.
(And, as it turns out, a 75 Ohm "video cable" will work quite well as an audio interconnect.)
In fact, virtually all commonly encountered coaxial cables have characteristic impedances of either 50 Ohms or 75 Ohms...
And either of those works just fine for regular audio signals.
In other words:
SOME BUT NOT ALL analog audio interconnects will work well for video signals.
SOME BUT NOT ALL analog audio interconnects will work well for DIGITAL audio signals.
BUT VIRTUALLY ALL VIDEO CABLES OR DIGITAL AUDIO INTERCONNECTS WILL WORK WELL AS ANALOG AUDIO INTERCONNECTS.
(But there is nothing that makes video interconnects or digital audio interconnects significantly better for carrying analog audio.)
There is one other thing worth mentioning...
The fact that a cable is properly impedance matched DOES NOT mean that it is efficient at delivering most of the signal to the load.
An impedance matched cable will deliver a CLEAN signal... but there are usually significant losses in signal LEVEL... which vary with frequency.
For example, at 55 mHz, a 100 meter length of RG-59, which is commonly used for cable TV, loses about 3/4 of the incoming signal strength (6.4 dB loss).
(The important thing is that the signal that makes it through arrives without significant signal corruption...)
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KeithL
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Post by KeithL on Aug 25, 2022 16:15:43 GMT -5
I should have mentioned that our new RCA cables are very nice. They're quite fat, but also extremely flexible, and the outside covering has a cool sort of rubbery feel to it. (And, of course, they WORK really well... but that goes without saying.)  |
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KeithL
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Post by KeithL on Aug 25, 2022 16:30:28 GMT -5
I should mention something somewhat important here... RCA cables have only two basic electrical connections... The signal - which goes through the center conductor and the center pin on the connector... And the ground - which goes through the shield on the coax cable and the shield on the connector... (This is true for all standard unbalanced RCA cables... because there are only two electrical contacts on an RCA connector... but NOT true for balanced XLR cables.) Some RCA cables may use a separate "ground lead" and "shield"... And, in that situation, the shield may be isolated from the ground lead, and may only be connected at one end... And there are situations where you may choose to "lift the ground", at one end, on one or more cables... However, in general, you MUST have one or more ground connections between different audio components... In most cases you CANNOT "just disconnect all the grounds at one end" or more or less terrible things may happen. (The kinds of things that can range from impossible-to-track-down hum to blown speakers...) In other words it is a really bad idea to start disconnecting ground connections unless you know exactly what you're doing and why. However there is another more commonly encountered sort of silliness these days... Certain manufacturers are determined to convince audiophiles that the copper wire itself is somehow "directional"... They insist that the "special" copper wire used in their interconnects carries an audio signal better in one direction than the other... And, based on this claim, they put arrows on their cables showing you which way to face them... This is, of course, complete silliness, and unsubstantiated by any legitimate engineering theory... (And, no, I've never met anyone who could hear a difference in a real double-blind test either.) IIRC the ones with the arrows means the shielding is only grounded at one end. |
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Post by DavidR on Aug 25, 2022 16:50:03 GMT -5
I should have mentioned that our new RCA cables are very nice. They're quite fat, but also extremely flexible, and the outside covering has a cool sort of rubbery feel to it. (And, of course, they WORK really well... but that goes without saying.) No specs given on wire used and shielding. @keithl > Could you enlighten us. I'd like to support the company that provides this site.
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Post by Boomzilla on Aug 25, 2022 17:07:24 GMT -5
Audio amigo who is a wire nerd prefers wires with multiple strands. He also prefers litz wire where the strands are individually insulated and electrically joined only at their terminal ends.
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DYohn
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Post by DYohn on Aug 25, 2022 17:22:58 GMT -5
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Post by AudioHTIT on Aug 28, 2022 13:17:46 GMT -5
Thought I’d tack a question on to this thread … I like to build my own cables for a few reasons: they are exactly the right length I need, I can use whatever type of connector I like and they’re consistent, I can usually use a thinner cable which makes cable management easier, all the cables have a consistent look (techflex, shrink tube, pants, etc). I currently need to build a few RCA cables, and would like to use some Belden 8451 I have around and normally use for balanced / XLR cables. One of the cables is ‘special’ in that it will be a short 15” run from my turntable to phono preamp. The other two are relatively ‘normal’, 4’ phono preamp to processor, 8’ Zone out to Zone amp. It might be desirable to wire the short phono cable differently (though the short length may also make it irrelevant) While the Rane Connection Guide is typically the reference for this sort of thing, it doesn’t take capacitance into account, so I thought I’d see if anyone has thoughts on which of the four possible wiring options below would be lowest capacitance? The first one is what Rane recommends, but their focus is shield and ground. Belden 8451 SpecsThe black box represents the cable with two conductors (red and blue) and a shield (green), the Yellow U shape represents an RCA connector, S is for Source, D for Destination  |
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