The more we talk, the more I think we are saying the same thing two different ways. EXCEPT, one of us is a little screwed up on the modes/scales terminology, and I seriously wouldn't doubt that it is me. However, to get an A mixolydian scale, I THINK what you would do is play the notes from the A major scale starting on the 5th of the scale, so you would get the following:
I just wanna get you straight on one thing there. To get the Mixolydian you start on the 5th note of the scale. You put that but you put to get A mixolydian start on the 5th note in the A major scale. That wouldnt be correct. You would start on the 5th note of the D major scale. Or you could just know that to get mixolydian flatten the 7th note. 7th note of A major being G# just make it a G and voila!