popping noise when hu is turned on

installed a interfire 4 channel amp into a 2001 ford f-350 with a sony hu and gravity componets in front and coax in rear when turning hu on the speakers have a popping noise but when you disconnect the rear speakers from the amp the noise goes away .  I even unplugged the rca plgs for the rear and left the speakers hooked up the noise was still there. tried other speakers and other wire still the noise is there, what else can i try or is the amp bad.beginner

Depends on what you mean by a popping noise, is it just a quick noise when you turn the car or HU on? or is it a sort of continuous static?  If it is just a quick pop its probably just turn on pop which is nothing to worry about, you could get a delay for it but really nothing to worry about. 

its just a quick pop, where would i get a delay.  Thanks so much for the helpbeginner

www.davidnavone.com he has a few turn on delays on his website, relatively inexpensive.  Like I said though, it you dont want to get one, it really wont hurt anything to leave it as is, my setup has had a turn on pop for two years now and its all fine.