This is a followup from a previous question: Analysing signal unbalancing stage which was quite broad as it encompassed couple of things, but answer there pointed me in the right directions so I'm able to pursuit further.
However, one particular thing is still a mystery to me:
The In+ and In- are voltages of the balanced audio line signal (https://en.m.wikipedia.org/wiki/Line_level) - meaning 600Ohms impedance and +4dBu level. What's the role of the capacitors? The answer to previous question suggests it is to block RF signal, so how do that work?
As far as my knowledge goes, those caps provide hi-impedance path to ground for the audio signal (the combined reactance for both input lines would be around 42pF, which, for the audio range would provide reactance of 190M to 190K), so only the negligible amount of signal would go that path (not sure what reactance the transformer coils provide, but probably small compared to the caps). If we take it that it's supposed to act as a shield against RF, then what would be the theoretical basis for that and how would that work? The reactance for RF frequencies would be much lower so they'd be shorted? But isn't the noise cancelled anyway because In+ and In- are inverted polarity, so noise inducted along the cable is cancelled (we sense the voltage difference between those).
The broader context:
I'm analysing a particular schematic, an audio compressor: https://www.soundskulptor.com/en/proddetail.php?prod=LA502
The schematic is here: https://www.soundskulptor.com/docs/la502-schematic-03.pdf