Cool. I'd like to try something similar. Does that amplifier module drive headphones as well? What future replacement do you have in mind? Is it all low power enough to use a battery?

For a headphone you do not even need the amp. The pcm5102a purple module can directly use headphones. Mine already has a 3.5 jack . It has been a life saver for devlopment at night.

I am planning to replace the amp with a Pam84xx and switch to a smaller/thinner speaker to save space. I may also add a nfc reader module to add nfc card music. Probably card will include a url to download music file.

Also my protoboard based solution is finicky. I starded building a pcb, however as this is my first pcb project I am taking it real slow.

Perhaps I can open a git repo to document share what I have.

I am open for suggestions for features.

Oh interesting. The datasheet for the PCM5102A says it supports line-level output with a minimum load of 1kΩ [1]. I think most headphones typically have an impedance of less than 100Ω. I'd guess the excess current results in some distortion or low volumes? It works fine in practice though?

[1] https://www.ti.com/document-viewer/pcm5102a/datasheet

I only checked it with a mdr-zx770bn. And it was OK. But as I did check that with a breadboard, any noise could be attributed to bad connections/emi.

Now I'll check it when I work on this next time. Probably in the upcoming days. ( Still my current protoboard would be only a tad bit better )

I rechecked it. There is no noise or distortion. In fact volume levels are pretty good. I am using some digital volume control and can't go too high.