Maybe it's useful for someone. I build a simple library for PT2313 chip from Princeton Technology Corp, a inexpensive audio chip with 3 stereo input, volume, bass,treble,loudness,gain and 4 outs. I have 2 amped speakers from Creative at home with electronics out of order and replaced with this chip and simple ClassD amp and a micro, it consume much less than before and have now better sound and was fun to build up. It should work with any arduino or teensy.
https://github.com/sumotoy/PT2313