As indicated by ham users the schematic is low quality in the PDF article released by TAPR. Here sharing a better quality picture, hopefully that helps.
Didn’t find an elegant compact solutions out there. I’m using only the GPIO pins, no need to route the audio jack output back to the PCB like existing solutions. Also using an on board amplifier which supplied from RPi 5V. Built a few prototypes yet and working nice 🙂 Enjoy! https://github.com/rfsparkling/RPi_Speaker https://www.reddit.com/r/RASPBERRY_PI_PROJECTS/comments/55hk5k/rpi_speaker_an_open_source_fully_integrated/