I think I raised this question back in the Pro5 days ... either I don't remember the answer or it didn't help me out ... since it's still an issue in Studio6, I'll float it out there again:

If I apply a simple MM-supplied plug-in like Chorus to a track, that track then undergoes a significant decrease in volume ... what causes this, more importantly, is there a cure other than just not using the supplied plug-ins.

I know that BlueLine (I think it's called) has some fans and also Ozone, and I can use those (and really like Ozone), but I'd still like to understand what causes the volume to drop when using the basic plug-ins.

When I used to use external processors for adding reverb to voice or to instrumentations in recording studios. I would always know that I would have to increase the volume to compensate for the drop of volume the sound processors would cause.

I beleive that once "clean" sound get's processed, it get's "filtered". The good thing is that many plugins and processors have a gain volume control built in. This way if you see that by adding a sound processor/plugin decreases the volume by a -1 or -2dB in your VU meters. You can increase the gain volume that exists in the plugin to bring back the target volume in your VU meters.

I think this post would do better justice in the Plugins section of the forum.