✔ 最佳答案
You are really some kind of brave soul. DIY while you don't know how to handle double shielded cable.
圖片參考：
http://hk.yimg.com/i/icon/16/4.gif
Unlike coaxial cables, the RCA cable (twisted pair) outer shield should only be grounded at one end, typically the low impedance signal source end. The other end has to be left unconnected. This is the reason why interconnect cables with shieldings are all unidirectional.
Differences in feature and parameter between RCA cables and coaxial cables?
While I can see what you mean by RCA cables but conceptually, we don't call those with RCA plugs RCA cables. We call them interconnect cables. Coaxial cables use RCA plugs too. It would be very confusing if you deem those cables with RCA plugs as RCA cables.
Coaxial cable is an electrical cable consisting of a round conducting wire, surrounded by an insulating spacer, surrounded by a cylindrical conducting sheath, usually surrounded by a final insulating layer (jacket). It is used as a high-frequency transmission line to carry a high-frequency or broadband signal. Because the electromagnetic field carrying the signal exists (ideally) only in the space between the inner and outer conductors, it cannot interfere with or suffer interference from external electromagnetic fields.
圖片參考：
http://upload.wikimedia.org/wikipedia/en/9/92/Coaxial.png
If you are doing coaxial cable DIY, coaxial cables must have the shield connected at both ends, as it supplies the ground return path for the signal. This is why the shield braid can and will affect the audio quality.
Most of the interconnect cables adopted twisted pair cabling method. Twisted pair cabling is a form of wiring in which two conductors are wound together for the purposes of canceling out electromagnetic interference (EMI) from external sources and crosstalk from neighboring wires.
Twisting wires decreases interference because the loop area between the wires (which determines the magnetic coupling into the signal) is reduced. In balance pair operation, the two wires typically carry equal and opposite signals (differential mode) which are combined by subtraction at the destination. The noise from the two wires cancel each other in this subtraction because the two wires have been exposed to similar EMI.
2007-05-03 09:43:12 補充：
Best telescoping shield cables (true telescoping shields) are constructed so that they have two shields which are insulted form each other. The idea is that you connect the inner shield to ground only at receiving end and the outer shield to ground only at the transimitting end.
2007-05-07 09:17:54 補充：
The purpose of the shields is to provide shielding for the cables. If you connect you inner and outer shields at both ends, the cable would become an antenna, much worse than having no shielding. That would defeat the purpose of having shields.
2007-05-08 12:59:29 補充：
For coaxial cable, the shield is connected at both end forming a signal return path. Does it also has an antenna effect?Exactly. That's why the shielding materials for Coaxial cable is very important.
