Same story as the perennial question of whether you can connect 2 amps directly to the same speaker even if you use only one amp at a time. If you connect the two sources to an amp which lacks a selector switch to select bal/unbal, the two sources will shunt each others output even if only one is in use at a time. Even with the switch, which probably only changes the ground connection, this is not likely to be successful.
I suggest you ask Levinson before trying this.
I suggest you ask Levinson before trying this.