Last year when I did a lot of sound-related projects, I implemented the YM3012 DAC on a Pico: https://blog.qiqitori.com/2023/03/raspberry-pi-pico-implemen... I used PIO to read the digital input and used PWM for the sound output. I verified that the conversion was correct but unfortunately never really put in a lot of effort to try to make it sound good. There's a bit of a hiss.