What may be a little confusing is that not all RCA cables are balanced + shield, but are in XLR.
In other words, the better RCA cables have two identical conductors, except the insulator color, typically red and black. One goes to the center pin, the other to the outer ring.
In addition to these there is actually a third conductor, not identical. Best are an impossibly thin foil shield, which is in contact throughout it's length to a drain wire. The shield is impossible to solder to, so we use that drain.
So, red and black connect at both ends. The drain however only at source.
Cheaper RCA cables use 1 wire, plus a braid. The central wire goes from pin to pin and braid does double duty as signal and noise.
There are minor tradoffs as the shield adds capacitance while preventing noise, but it's usually well worth it.
Best,
Erik
