Пакет alsa-plugins-equal: Информация

Alsaequal is a real-time adjustable equalizer plugin for ALSA. It can be
adjusted using an ALSA compatible mixer, like alsamixergui or alsamixer.

This configuration (/etc/asound.conf or ~/.asoundrc) works fine for me:

ctl.equal {
    type equal;
}
pcm.plugequal {
    type equal;
    slave.pcm "plug:dmix";
}
pcm.!default {
    type plug;
    slave.pcm plugequal;
}

Adjust equalizer settings:
$ alsamixer -D equal