Something

pcm.nforce-hw {
type hw
card 0
device 2
}

pcm.!default {
type plug
slave.pcm "nforce"
}

#0,0 is analog out (i.e. headphone socket on the shuttle), and 0,2 is
#spdif out.

pcm.nforce {
type dmix
ipc_key 1234
slave {
pcm "hw:0,2"
# pcm "hw:0,0"
#period_time 0
#period_size 1024
#buffer_size 4096
#rate 44100
}
}

ctl.nforce-hw {
type hw
card 0
device 2
}