I have an svt 3 pro, going through a 4ohm 4X10 cab. Recently the peak light will come on and my bass will cut out. It usually lasts a few seconds. Sometimes it stays on till I give the head a tap. Well today during band practice it cut out compleatly and wouldn't come back on. The amp was still running fine just no noise. I could turn the amp off then back on and it would work for a min then cut back out. So today I bought new tubes. Still no fix. My bass is passive, so no battery problem, amp fuse is good, new tubes, cable is good. What now?