I've got a bass with an 18 volt Aguilar preamp installed by the luthier. When I engage the preamp I get a extremely loud "POP". Loud enough that I won't switch back and forth for fear of damaging my speaker. I've had several Laklands with the 9-volt bart preamp and this was never as noticeable a problem. You definitely heard something, but nothing of concern. Is this normal with the Aggie or can it be remedied?