pcm.!default {
        type plug
        slave.pcm "mdev"
        route_policy "duplicate"
}

pcm.mdev {
        type multi

    # hw:0,0 - loopback device. Compiled into kernel. (ALSA->Loopback...)

        slaves.a.pcm "hw:Loopback,0,0"
        slaves.a.channels 2
        slaves.b.pcm "dmixer"
        slaves.b.channels 2

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

pcm.dmixer {
        type dmix
        ipc_key 1024
        slave {
        # hw:2,0 - external USB audio box.
                pcm "hw:2,0"
                period_time 0
                period_size 1024
                buffer_size 4096
                rate 44100
                channels 2
                format S16_LE
        }
}

ctl.!default {
        type hw
        card 1
}