Mine

pcm.card0 {
type hw
card 0
}
 
pcm.!default {
type plug
slave.pcm "dmixer"
 
}
 
 
pcm.dmixer {
type dmix
ipc_key 1025
slave {
pcm "hw:0,0"
period_time 0
period_size 1024
buffer_size 4096
periods 128
rate 44100
}
bindings {
0 0
1 1
}
}

pcm.duplicate {
    type plug
    slave.pcm "surround51"
    slave.channels 6
    route_policy duplicate
}
pcm.ch40dup {
    type route
    slave.pcm surround40
    slave.channels 4
    ttable.0.0 1
    ttable.1.1 1
    ttable.0.2 1
    ttable.1.3 1
}