SinOsc a => dac.chan(0); // send sine wave to the fourth mono output

while(true) {
    1::second => now;
}
Now,start it up like any plain old chuck programs, without trying to make use of multiple outputs or anything:
chuck test.ck
Do you hear a low sine wave? Fine, the app works. Now try the same program with a different setting:
chuck --out4 test.ck
Do you still hear the sine wave? Do you get an error message, and if so, which one? Do you get silence? Do you have some kind of meter LEDs on your soundcard (or in a mixer program on your host), and if so, can you see any of the meters going up? What soundcard are you using by the way?
Depending on what your answers are to the questions above, you may move ahead with specifying --adc and some number. If you got the above working, just increase the number of outputs to what you want. If you can't get it working, post the output of chuck --probe here and I or someone might get some other idea...
/Stefan