I've noticed on my New model GMC-300 the CPM Changes With Speaker On/Off Setting. I'm not moving the unit from the source, and I can repeat this constantly.
The CPM reads Higher with the speaker on, which is confusing because if the speaker drained a lot of power it would the CPM would be lower right?
The backlight has no effect on this, neither does running it off of ac power, it still reads higher with the speaker on.
For instance:
3000 CPM Speaker Off
4500 CPM Speaker On
I made a video of it doing this.
www.youtube.com/watch?v=EM99j8YBOho