Phat DAC down-mixed to mono audio

Hey guys,

I'm trying to use my Phat DAC in a mono speaker setup, as an airplay receiver.
I have the Airplay part working great with the Phat DAC, and it sounds great!

However, I'm having some problems getting the Phat DAC setup to down-mix to mono.

I found the following page online:
http://alsa.opensrc.org/Asoundrc#Downmix_stereo_to_mono

Which says to change /etc/asound.conf to the following:

pcm.!default makemono

pcm.makemono {
    type route
    slave.pcm "hw:0"
    ttable {
        0.0 1    # in-channel 0, out-channel 0, 100% volume
        1.0 1    # in-channel 1, out-channel 0, 100% volume
    }
}

However when I do this, I now don't any audio at all. Is there something I'm missing? Or is the Phat DAC bypassing some of these settings somehow in it's setup?

Any help would be appreciated!