I have a loud interference noise coming from my speakers when the car is running after a new sound system installation.

I have a 4 channel amp running four speakers in parallel on the front two channels and the two rear channels bridged running a sub. The weird thing is the noise only happens when both sets of RCA's are plugged in. If I unplug one set of RCA's the noise disappears, it does not matter which channel I unplug or which RCA cable as long as I unplug one of them the noise goes.

There are no problems when ignition is on acc or on position but as soon as I start it the noise appears. It does not matter where the volume level is the noise stays consistent.

The amp is mounted behind the rear seats in the boot. I ran the power wire down the centre of the car and the rca's down the passenger side but have since pulled them out having them just run over the top my seats to make sure they aren't near any power wires. The amps ground is on one of the rear seat bolts with the paint sanded away. I tried grounding the HU to the same position as the amp and it did not make any difference.

Anyone have any idea's of what I should try next or what the problem could be?

 

Well a few days late but ill give this advice... make sure your main power contacts fully connected and 100% clean. When you ground the radio and amplifier correctly, every connection has to be made perfect. The rca wires can be very delicate. Make sure that all the wires are secure and fully connected. I do believe that there is a filtration system for this issue. Just in case none of this works.

 

Re-do the ground wires. Is the power wire sufficient....as in the correct size for the amp? Undersizing the power wire will cause issues.