For optimum performance the DA-2 should be connected to an unbalanced input using only pins 1 and 2. Pin 2 should connect to the signal conductor and pin 1 should connect to the ground or return. The signal level is then halved.
NOTE : Use of output pin 3 instead of 2 will result in phase inversion.
It is possible to drive unbalanced inputs from pins 2 and 3 but this unbalances the output and can lead to hum. In any case do not connect any of the three output pins to each other.