[InazumaDenki] wanted to answer the question: can you drive a motor with an audio amplifier chip? The answer, of course, is yes. The TDA7052 has a single input, and a bridge output meant to drive a speaker differentially. It should work if the motor doesn’t present more of a load than a speaker.
The plan was to use a resistive divider to provide several discrete voltages to the input. At precisely the half-way mark, there should be no voltage across the load. Altering the input to go higher than halfway should make the motor turn one way, and making it go lower should turn the motor the other way. As you can see in the video below, it does work, although it may not be ideal for this application.
By varying the voltage at the input, the motor changes speeds, although this won’t be as efficient since you probably would prefer to control the speed using PWM to preserve the motor’s torque output. Since the motor is a very inductive load, the circuit has didoes to trim back kickback voltages to protect the device.
Still, it is an interesting idea, and if you are only interested in direction control, it probably isn’t a bad thing. Feeding PWM through the device might be difficult, though, since it would have to be referenced to the midpoint, not ground. Otherwise, the motor would just spin in one direction for a bit and then back in the other direction — not really what you want.