Alsa sound configuration in /etc/asound.conf

asound.conf

# virtual PCM pointed to by !default
pcm.plugequal {
  type equal;
  # Software mixing through dmix. All sources played at once
  slave.pcm "plug:dmix";
}

# The sounds are processed with an equalizer
# another alsa plugin
pcm.!default {
  type plug;
  slave.pcm plugequal;
}

# This enables to set the equalizator settings
# by enabling the control
ctl.equal {
 type equal;
}