ALSA config for custom recording device (that also outputs to speakers)

.asoundrc

# create default device, outputs to just audio out
pcm.!default {
    type asym 
    playback.pcm "plug:dmix0" 
    capture.pcm "dsnoop:PCH"
}

# outputs to both audio out and loopback
pcm.record {
	type asym
	playback.pcm "plug:both"
	capture.pcm "dsnoop:Loopback,1"
}

# software mixer for audio out
pcm.dmix0 {
    type dmix 
    ipc_key 1024
    slave {
        pcm "hw:PCH"
        period_size 256
        buffer_size 1280
    }
}

# software mixer for loopback
pcm.dmix1 {
    type dmix
    ipc_key 2048
    slave {
        pcm "hw:Loopback"
        period_size 256
        buffer_size 1280
    }
}

# plays to both audio out and loopback
pcm.multi {
	type multi

	slaves {
		a { pcm "dmix0" channels 2 }
		b { pcm "dmix1" channels 2 }
	}

	bindings {
		0 { slave a channel 0 }
		1 { slave a channel 1 }
		2 { slave b channel 0 }
		3 { slave b channel 1 }
	}
}

# magic routing???
pcm.both {
	type route
	slave.pcm "multi"
	ttable.0.0 1
	ttable.1.1 1
	ttable.0.2 1
	ttable.1.3 1
}