BALUN for differential to single conversion

I need to convert differential data signal to single ended signal using isolation transformer

The transformers must work at low frequencies also and these are interfaced with op amps output and op amp input. 

Can you please tell me the use of resistor configuration at transformers output and inputs.

experiment done : In image, first transformer part number : MABA-007159-000000 (link : and second transformer part number : MABAES0060 (link :
Now, I am giving input(-2.5V to +2.5V sine wave , 32KHz) from function generator and the output is observed at osciiloscope.
Observations :
The signal amplitude was attenuated at 32KHz, 320KHz, 200KHz
at 5MHz the output was same as input but at >15MHz, output was amplified.

Now I swapped the input and output. same procedure was repeated , same observations were made.

can you please suggest any part numbers for achieving this application
The circuit should work in bi-directional way i.e input should act as output also and output should act as input also i.e when data is fed at data+ and data-, this circuit should convert the signal to single ended , when input is O/P in first image then it should convert the single ended signal to differential signal.
The frequency of signal is 32KHz and signal is -12 to +12V square wave.