Mine

pcm.casqueusb_hw {
	type hw
	card 1
}

pcm.dmixer_cusb {
    type dmix
    ipc_key 1024
    slave {
        pcm casqueusb_hw
        period_time 0
        period_size 1024
        buffer_size 8192
        #periods 128
        rate 44100
     }
     bindings {
        0 0
        1 1
     }
}

pcm.casqueusb {
	type plug
	slave.pcm "dmixer_cusb"
}

ctl.casqueusb {
	type hw
	card 1
}

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

pcm.dsp0 {
    type plug
    slave.pcm "dmixer_cusb"
}

ctl.!default {
		type hw
		card 1
}


ctl.mixer0 {
    type hw
    card 1
}