I'd forgotten about U11; this is an alternate pinout for a Cirrus CS4341 DAC. ISTR that the package is bigger and so it'll be easier to pick signals off it.

SDATA is pin 2, SCLK is pin 3, LRCLK is pin 4 and MCLK is pin 5. If you need it (at 3.3v), pin 6 is I2C SCL and pin 7 is I2C SDA.

There's no digital 5v on the board; any CS8405 board is going to need 5v, so you'll have to regulate it down from the 12v supply on the main board. There *is* a 5v linear regulator supplying the DACs, but this is supposed to be a clean DAC feed...

Hope this helps!

Hugo