[TenTec] Orion mic input question

[w9ge]

I have finally, after a year, hooked up my scope to the rf chain from my Ten Tec Orion.  It appears the mic gain setting has no affect after turning it past "15".  I have been running my Heil HC4 element with mic gain at 65 with no known ill effects, and noticed the same on the scope with it as with a two tone test signal inserted in the mic jack.  No change in rf output with mic gain set anywhere between 15 and 100.  I can vary rf power out with the power control just like on cw.  

Is the Orions internal ALC for mic gain that good?  Or am I missing something?  If what I see on the scope is correct it is likely almost impossible to overdrive the Orion on voice.  I appreciate the wisdom of ssb ops who know more than I about mics and mic inputs etc.  thanks.  73 bob de w9ge