question, i have a warwick streamer stage 1 (1998) with basslines soapbars and whatever preamp it came with (mec?). after about 15 mins. of playing the signal drops by about half. it has done this with 3 different amps, and only does it in active mode. it starts to caome back in and fade out. what could it be. the batteries are new. i'm about to put a bartolini pre amp in it. thanks for the help.