[joethefox]

I made it through Alsaequal and at the moment you can control it via a linux console shell.
Tested in a Ubuntu Maverick 10.10 installed with this guide: XBMCbuntu.

Download alsaequal from www.thedigitalmachine.net (direct link)
to successfully compile in ubuntu I had to install these dependencies

Code:

$ sudo apt-get install libasound2-dev caps

then

Code:

$ tar xvjf alsaequal-x.x.tar.bz2
$ cd alsaequal-x.x
$ make
$ sudo make install

if all goes well we now have installed alsaequal. To use it with XBMC I create /etc/asound.conf with the following content:

Code:

pcm.!default {
  type hw
  card 1
}

ctl.!default {
  type hw
  card 1
}

ctl.equal {
  type equal;
}

pcm.plugequal {
  type equal;
  slave.pcm "plughw:1,0";
}

pcm.!default {
  type plug;
  slave.pcm plugequal;
}

NOTE that I use CARD 1 and plughw:1,0 because my dac (usb soundcard) is identified by 1, you can see which is your soundcard number with aplay -l.
NOTE2 (thanks to muzzol) if you want to configure it just for your user you can use ~/.asoundrc.

I finally selected in XBMC "Default" as Output device (under SYSTEM>AUDIO OUTPUT> AUDIO OUTPUT DEVICE) and now via console I can control XBMC audio output with a real-time adjustable equalizer:

Code:

$ alsamixer -D equal

output