Someone

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

pcm.dmixer  {
        type dmix
        ipc_key 1024
        slave {
            pcm "hw:0,0"
            period_time 0
            period_size 1024
            buffer_size 8192
            rate 44100
        }
        bindings {
            0 0
            1 1
        }
    }