Using parametric equalizer with software mixer in alsa

The full contents of /etc/asound.conf:

pcm.dsp {
    type plug
    slave {
        format FLOAT
        rate unchanged
        pcm {
            type ladspa
            channels 2
            path "/usr/local/lib/ladspa"
            playback_plugins [{
                label "ladspa_dsp"
            }]
            slave.pcm {
              type plug
              slave.pcm {
                    type dmix
                    ipc_key 1234
                    # Xenix 302USB
                    slave. pcm "front:CARD=CODEC,DEV=0"
                    # built-in
                    #slave. pcm "hw:1,0"
                    bindings {
                        0 0 # from 0 => to 0
                        1 1 # from 1 => to 1
                    }
                }
            }
        }
    }
}
pcm.!default {
        type copy
        slave.pcm "dsp"
}