Something

pcm.dmixer {
    type dmix
    ipc_key 1024
    ipc_key_add_uid false
    ipc_perm 0660
    slave {
        pcm "hw:0,0"
        rate 48000
        period_time 0
        period_size 1024
        buffer_time 0
        buffer_size 5120
    }
}

# change default device:
pcm.!default {
    type plug
    slave.pcm "dmixer"
}