the Channel Mode Button is at the same position as the Input Selector on a Channel Strip.

When you click on it, it splits the single Stereo Output Channel Strip into two Mono Output Channel Strips. This is very handy for other purposes, but not for making quick mono mixes. You still have a stereo mix, just with the left and right channel on different Channel Strips.
Use the Gain Plugin as Indyuser suggested. However, keep in mind that when you bounce your project to an audio file, this will still create a 2-channel file (be careful that a 2-channel audio file is not necessarily a stereo file, and mono doesn't mean 1-channel)
Hope that helps
Edgar Rothermich - LogicProGEM.com
(Author of the "Graphically Enhanced Manuals")
http://DingDingMusic.com/Manuals/
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