This is really cool, I'm doing something similar! I'm making synthesizers with the Uno and Due; I haven't tried doing anything with audio input yet, but want to play with that as well. How is the sound quality of it? I did the 8-bit resistor ladder DAC from the instructable linked, but quickly broke the layout when I tried to bring it to a friend's house and haven't tried putting the breadboard back together. I really should go back to that, I liked how crappy it sounded. I also tried making a 1-bit DAC out of it, which worked better than I expected (though it still wasn't good, I just didn't expect anything haha).
Now I'm using the Due and Teensy (Cortex M3 / M4) because of the hardware DAC and 32 bit processor. I haven't gotten filters working yet either, they are my next goal. IIR first, and then FIR if the Due can handle it. But I have gotten a cool resonant filter simulation by using a hard-sync as described here [0]. You get some neat variations by changing the waveshapes used and the windowing function. I might not even have subtractive filters in my final design, just because of how cool it sounds to approach it differently, but I still want to understand how to implement them.
Nothing on Github to share at the moment, unfortunately. I'm too embarassed by the state of the code, lol. But I will be checking out your project this weekend, so thanks for sharing!
Thanks! The sound quality of it depends mostly on the sample rate it is able to achieve, which is somewhere around 9.6khz if all it's doing is reading a sample and then outputting it to the DAC. At 6bit 9.6khz a guitar sounds surprisingly clean through it, aliasing is only really noticable at the highest frets of the high strings. At lower bit depths and sample rates it gets really interesting.
Getting the best sound quality out of it also depends on finding the sweet spot on the input gain to get the best dynamic range from the DAC without clipping, although I designed the preamp to sound pleasant when overdriven, mostly using JFETs.
Now I'm using the Due and Teensy (Cortex M3 / M4) because of the hardware DAC and 32 bit processor. I haven't gotten filters working yet either, they are my next goal. IIR first, and then FIR if the Due can handle it. But I have gotten a cool resonant filter simulation by using a hard-sync as described here [0]. You get some neat variations by changing the waveshapes used and the windowing function. I might not even have subtractive filters in my final design, just because of how cool it sounds to approach it differently, but I still want to understand how to implement them.
Nothing on Github to share at the moment, unfortunately. I'm too embarassed by the state of the code, lol. But I will be checking out your project this weekend, so thanks for sharing!
[0] https://en.wikipedia.org/wiki/Phase_distortion_synthesis#Sim...