"Logan Shaw"
"Mike Rivers".

Common mode rejection is the ability to reject noise that's common to
the two wires of a balanced input. An example is RF interference
that's picked up by both wires equally.

** That not a correct example. RF interference is defeated firstly by
the use of shielded cable and secondly by the use of filters to reduce
such
signals at the inputs of the balanced pre-amp.

Common mode rejection operates across the audio band and maybe a little
beyond but is usually most effective at the lower frequencies since the
main
aim is to eliminate ground hum from audio systems. A ground hum voltage
will
appear equally on the two wires and so be rejected.


So why is it you think that RF can't exist at audible frequencies?


** RF = "radio frequencies". Radio frequencies are those used for radio
communication - ie much higher than audio frequencies. The term Mike used
was " RF interference" - which refers to unwanted injection of RF energy
into a circuit.


Even if it's caused by A/C current and at 50 or 60 Hz, it's still
radio noise picked up by the wires because they're acting as antennas,
right?


** No. The wires inside the cable are acting as an induction loop in
magnetic field while frequencies concerned are in the audio range.



.............. Phil