Twisted RCA's never CANCEL noise, they simply reject most (or some) or the noise that can be induced.

I have never seen a head unit or amplifier in car audio (doesn't mean it doesn't exist) that uses differential inputs, and if it did it would not be through an RCA connection (in pro audio its usually through XLR). Differential needs 3 conductors, a signal +, signal -, and grnd. All RCA connected signals are single ended, unbalanced, whatever you want to call it.

With a balanced signal the cable is not what is rejecting the noise, the technology/hardware is. At the source end, the original signal is send down signal +, the inverted signal is sent down signal - and the foil is the reference grnd. At the recieving end the signal - is inverted again and the 2 signals are summed. This means that any signal that is not the exact same on both signal + and signal - is just induced noise and is rejected. Don't confuse this with processing either, this is all done through a simple analog opamp at either end.

Darn shame they don't use balanced signals in car audio. I use it whenever I can in home audio, and it was almost always used when I did pro audio.

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