My OPINION.... Even if electronics are fully balanced from end-to-end,
it doesn't matter. The "balanced" effect is all myth and hype. Noise
is NOT appreciably reduced since it is in the system REGARDLESS of the
design of the interconnects. It is just there. Shielding is the only
way to help reduce noice, but it will not STOP noise. So the bottom
line is balanced is a complete myth and waste of money. Better to spend
money on good single-ended components with top performance rather than
wasting it on balanced components.
Opinion yes, fact- no.
Fact: a differential gain stage has up to 6db less noise than its single-ended counterpart. If you have more than one stage of gain, how many db less noise is possible then?
Fact: a differential gain stage has a spec called Common Mode Rejection Ratio (CMRR); if there is a noise common to both the inverted and non-inverted inputs, a differential amplifier with a high CMRR value will be shown to have far less of the noise signal (down by the value of the CMRR) while a single ended circuit will not. Our input circuits tend to be in the high 90s to low 100s in this regard.
Historically, the balanced line system is what made long distance telephone possible. It also ushered in the era of high fidelity, as for the first time the recording gear could be remote (not within 10 feet) from the performance being recording, without degradation. All of music is recorded with balanced line; its not hype.
