automating drum distortion

[gatorgrips]

I'm trying to mix a song right now and I want to put distortion on the drums, but only at the end of the song (the last 15 seconds or so).

The way I tried do this was by setting the output of the 4 drum tracks to an aux bus and putting antares tube on the aux track. Then I went into the plugin and put the master bypass to automation, but when I tried to draw the automation (on/off) it had no effect. It is constantly on.

Another way I could do this is to make a stereo audio track and record the drums with distortion on them on this secondary track. Then I would have to fade the regular drums out and the dist drums in at the end of the song. But that makes changing the distortion settings a bitch cause I would have to rerecord it every time I want to change the dist settings, so I would prefer to just automate the plugin.

But why the **** won't it listen to teh automation line? it just completely ignores it and i'm getting pretty frustrated. Is master bypass not what I think it is? Any ideas or suggestions would be awesome.