I used ecm-719 with just the battery in the back < jb3 and there is a lot of "extra noise" on the recording...
A battery box would most likely eliminate it...
I would recommend the battery box, thats what I am looking to do myself, as this distortion/static is noticable and pissed me off, but I am also getting rid of the ecm-719, it has just been a qwik fix, it is not very good quality at all to my ears...
just my opinion...