i'm trying to figure out, can you put two TWR-AUDIO-SGTL in one tower system to get 4 audio channels?
First, the processor must support it. I'm looking at the K70F120M, and that processor can mux I2S1 (the second I2S bus) to some various pins that go out to the TWR connectors (EBI, LCD) (note - not planning on using those for anything...)
Next, how to modify the second TWR-AUDIO-SGTL board.
Looking at the schematic, it looks like someone made an error the way the CTRL-ADR0-CS was connected (R20 serves no purpose if stuffed, except to generate heat). To make that go high (so you could address two SGTL on the same I2C bus) looks like you have to cut a trace.
The SGTL's I2S pins all go thru resistors so they could be isolated from the I2S0 bus and perhaps jumpered to some of these other lines... if I can figure out definitively the best place to route I2S1 from the processor....
MCLK looks like it can be synchronized with jumpers - one board can generate it, the other can select the bus and pick it off... or I can configure the K70 to be master if I can get the correct ratio with the PLLs...