I just installed a new 4channel amp in my car for my speakers. I also have a mono amp for my sub. The mono amp is connected to the 4 channel amplifier, but whenever I have the mono amp connected It makes a loud static beep/pop when I turn on/off the ignition. When I disconnect the subwoofer I get no beep/pop , but then I cant use the sub. I have grounded both amps and I use a splitter for my powercable to the amps. The signal wire runs directly from my 4 channel amp to my mono amp.