The device you need is called a compressor. When the volume of your signal goes above a level that you choose, it turns it down.

David French wrote: The device you need is called a compressor. When the volume of your signal goes above a level that you choose, it turns it down.

Does the threshhold setting allow you to increase the level at low db's or does a compressor allow you to do that?

Compressors only decrease level; however, the soft parts can be made to be roughly the same loudness as the loud parts. Then, the compressed signal can be turned up - this is called makeup gain.

thanks French!

Skillz:
I have found a relatively inexpensive compressor that works very well on podium mics (church, schools).It is the dbx 286a mic processor. It keeps the dynamics of "amateur" speakers in check. You can find them on e-bay for around $100.00 and they are a lot better than your typical fare from ART, Behringer, Samson, etc. Check one out.