How to change the polarity of 0~5 volts get -5~+5 volts?
All you need to do is connect your DAQ to the audio amp through a capacitor. This will remove any DC component from the signal. If the Amp side of the capacitor is at "0V" then the voltage will appear to swing -2.5V to +2.5V. I know that's not exactly what you asked for, but if your Amp has enough gain it should work. If you really need -5V to +5V then you will have to add an op-amp with a gain of 2. The good thing is that most audio amps already have a capacitor in their input circuit so you probably don't even need to add the capacitor!. If you need to add a capacitor then try a value of 100nF as a starting point.