I don't know if anyone else has had this issue, but my Ampeg amp works well alone, but the moment someone connects a three-pronged, microphone-style line from the "Line Out" slot on my amp (to connect to a PA system), the sound gets sucked out of the Amp. It plays on the PA system and the monitors, but the Amp's internal speaker loses its output. I've seen this happen with other bass amplifiers before as well. Does it have to do with the electricity flowing through both the PA and the BAss amp? Are they both mixing power through the wires and therefore causing a change in power controls (from the AMP to the Mixer head)? I would love to get my Amp working right so I could use my bass amp as a monitor on stage and also send a feed out to the PA system so that it goes out to the audience with more power. Thanks for the help!