I'm still seeking further understanding. Please correct me where I am wrong.
Common mode noise is noise that is added equally to both the + and - wires (for balanced), or both the + and ground wires (for single ended). When a headphone transducer rejects common mode noise, it does so equally well with both balanced amps, and single ended amps.
But is it the case that common mode noise is the same for both balanced and single ended signals? Certainly that is true for noise from electromagnetic interference. What about noise introduced by the amplification circuit itself? In a single ended amp, only the + signal is amplified. So noise from that stage will not be rejected by the transducer. In a balanced amp, any noise injected into the + signal will also be injected inversely into - signal. So that will get cancelled out. Correct?
Lastly, how would each of the following compare in terms of transparency (in theory, of course):
A. balanced DAC -> drop half -> single ended signal -> single ended amp
B. balanced DAC -> opamp -> single ended signal -> single ended amp
C. balanced DAC -> transformer -> single ended signal -> single ended amp
D. balanced DAC -> balanced signal -> bridged balanced amp
E. balanced DAC -> balanced signal -> fully differential balanced amp
I've listed it from worst to best according to my uninformed opinion. Did I miss anything?