There are a few things you can check.
First check that your input gain is set so that there is a good signal level but no clipping distortion.
Secondly, if you are running all your tracks in ALK directly to the output of your audio interface, it's possible that the combined signals could go over the 0dB mark and distort. I would recommend making another audio track and naming it "Main Out" or something similar, then sending all your other tracks to this track instead of the interface output. This way you'll be able to pull down this master fader on the "Main Out" track and avoid clipping.
Hope that helps.