Running a Bart MME through the two band pre-amp. Pre-amp came mis-wired from factory, fixed that, runs fine, then after 2-3 weeks and not playing frequently at all, the 9 volt is dead. Wondering if this means I need to run as an 18v? Is the pull position vol staying "on" when pushed in? Not leaving the bass plugged in or anything like that. Have used several 9 and 18v pre-amps and never had this prob.