On the day mini-amps were invented ... The speakers are wired to a simple aux jack and connect to an LM386 low-voltage amp circuit which [Olson] assembled and mounted into the header.

For instance, our other favorite DIP chip amp, the TDA7052, has been end-of-lifed. So for an SMT PCB design, the LM386 is dead. There are hundreds of few-hundred-milliwatt amplifiers out there ...