Mine

pcm.!default {
        type dmix
        ipc_key 1024  # any unique value
        ipc_key_add_uid false
	ipc_perm 0660 
        slave {
                pcm "hw:0,0"
                period_time 0
                period_size 1024  # must be power of 2
                buffer_size 4096  # ditto
        }
}