I think your problem with enough gain results from the battery box you are using; the MPS6000 series is merely a battery box, I don't think it can provide gain because there are no trim pots with which to do so; the MMA6000 unit however provides both phantom power and it provides variable gain since it has trim pots; you really out to go over to dpamicrophones.com to look at pics of all the units, its all there