Alsa Dmix wrong sample rate

Question

I am trying to add a dix to my Alsa conf file, but when I playback using it the sample rate is wrong (it's too slow)

I have the following:

pcm.dmix0 {
type dmix
ipc_key 34521
slave {
    pcm "hw:0,0"
    format S16_LE
    rate 48000
}
    hint {
            description "DMix of Card0"
    }
}

pcm.asym51 {
       type asym
       playback.pcm "dmix0"
       capture.pcm "hw:0,0"
}
pcm.dsp0 {
     type plug
     slave.pcm "asym51"
}

When I play the audio back directly to the hardware, it plays fine, but I do miss a bit at the start.aplay -D hw:0,0 /usr/share/sounds/alsa/Front_Center.wav

When I use my dsp0 / dmix the rate is much slower than it should be:aplay -D dsp0 /usr/share/sounds/alsa/Front_Center.wav

What am I doing wrong?