asterisk users - Jun 2009 - alsa no input

I have setup asterisk alsa.conf to read the null device for ALSA and 
console/dsp input.

asound.conf is
pcm.nullpcm {
    type null
}

alsa.conf has
 input_device=plug:nullpcm

Then when I call into the Console/dsp  I get very choppy audio.
I dont need and data from the microphone. I just want data out on 
console/dsp.

Have I not setup the device properly? why would I be getting choppy 
audio from
null pcm device? Is there a better way to accomplish ALSA input for the 
console/dsp channel?

Thanks,

Jerry