**The "standard solution" for "signals" (such as audio) is an RC- High-pass filter. ** The DC component is zero-Hz so it gets filtered-out. You'll get a voltage that goes from (about) -2.5 to +2.5V (assuming a regular 5V Arduino).
For AC "power" you'd need a different approach.
An H-bridge (or relay) can reverse the connections to reverse a motor (etc.) but the voltage doesn't go negative relative to ground so the motor (etc.) can't have a ground connection.
I should be able to use one of the analog input to do so I think. I guess I'll filter the signal to get it a bit smoother. Or do you have some other suggestions to how this could be done?
The regular Arduino doesn't have a true-analog output. analogWrite() is [u]PWM[/u] which can "simulate" analog to control the speed of a motor or to make an LED appear dim.
If the signal frequency is low compared to the PWM frequency it can be filtered to analog.* This time it's a low-pass filter, so combined you have a bandpass filter.
* Class D audio amplifiers use a kind of PWM in the MHz range. With class D amps, the pulse width is analog so there's no sample rate, just a PWM clock. The frequency is high enough that it (obviously) isn't audible and it doesn't interfere with the audio signal. There's usually an LC filter but some small-cheap class D amps don't bother with filtering. The inductance of the speaker coil does some filtering and the rest is filtered-out mechanically since the speaker cone can't move at MHz rates.