With regard to audio and balanced signals with XLR connectors, how does noise affect an unbalanced signal on the same cable that normally carries a balanced signal?
To give some background, I have a five metre cable run from an unbalanced source to a balanced amplifier that isn't using very good cable and is picking up a lot of audible noise. I can either replace it with better shielded unbalanced headphone-style cable, or move the RCA to XLR adapter closer to the source and then run two long balanced cables to the amplifier.
The better shielded headphone cable will improve the noise, and of course a balanced signal the whole way would be even better, but what about an unbalanced signal over the balanced cable?
Will the noise be worse, because the balanced cable has less shielding? (I'm assuming it has less because the balanced nature of the signal allows noise to be better cancelled.) Or will the unbalanced signal still benefit from the noise reduction applied to the signal at the destination? What if the source ties the unbalanced audio GND signal to the same chassis GND used for the cable shield - does that reduce the noise in one of the balanced lines, resulting in less noise reduction when the two "balanced" signals are recombined?
The reason I am asking is that I'm not sure exactly how an unbalanced signal is presented on a balanced input. There doesn't seem to be any active conversion taking place in many of the adapters you find online, so I'm not sure whether the amplifier needs to be designed to accept an unbalanced signal, or whether any balanced input can accept an unbalanced signal without any problems.