In our balanced amps, they had not the phase splitter to conversion the RCA to balance signal.
The real balanced amp design, can get the single-ended input and output balance signal without phase splitter .
The diagram as below.
The design can feed the single-ended to either either -IN and +IN input, or feed to both inputs,and had the +out and -out signal .
In the case , can avoid the new distortion of the phase splitter .
Sorry for the poor English may can't explain...