Whatever was bothering the board seems to have corrected itself. It works reliably and admirably now. The only change is that I rewired the digital out board (necessary to buffer the I2S signals) to digital supply and ground from analog supply and ground. Not sure why that would help.

What do people think would be a good voltage output level for this thing? I can go pretty close to five volts, but no higher. I will be ordering parts for an improved version pretty soon, so I need to figure out what value resistor I need for the gain to achieve the desired output level. So far one vote for 4 volts. RMS or P-P? The caps in the analog path will be poly, rather than ceramic and resistor will be precision .1% instead of 1% so so resistors. I may need to experiment with layout too in order to get the best sound.

So far highs are not real extended and the noise floor could be better, although it's better than many stereo components already. More updates to follow.

Stu