HELP genz benz 750 noise

Im having a hard time figuring out this static like crackle out of my rig.At first i thought it was the preamp to my active shcecter bass.I got a wierd pop when i made contact with the backplate.After replacing that and painting the shield cavity in the back it seemed ok for a while.Just a few minutes. then it came back.its odd because it doesnt do it first then it gets going and doesnt stop.I notice its when i turn the fader between pickups all the way to the left it stops.Could this be a bad pickup?I think its the amp head and not the cab because the sound comes out when i plugged in directly to a soundboard and both channels.I have a bg 750,Ampeg410hlf classic,and a shcecter studio 5 string.I use both channels often and have my bass turned most the way up as far as the preamp controls and volume.PLEASE HELP.Any ideas on my problem.

 

No.Its not a feedback type noise. It almost sounds like a blown speaker but it makes th same noise through direct recordings.

 

It happens when i play and seems to start when i hit a hard note.The amp doesnt make any noise without bieng pluged in.No effects and i have played with another bass.The noise didnt come back but it as also fine yesterday with my original bass.I dont know if its distortion.It sounds like crackling or hissing.I just had my bass checked top to bottom because I thought it was the bass.It would snap or hiss kinda like the sound im getting now when i made contact with the backplate.Painted the shield cavity and is fine now but i wonder if i caused damage somehow.My bass doesnt make the sound out of my other amps.