New radio now I have a hiss..Any experts?

So I disconnected my clarion radio and bought a JL MM100-BE. I installed my entire system, 2 Kicker MX400 amps and 1 JL sub amp. All new wiring ect....BEFORE I installed the new radio. I listened to my old radio for a month with no problems. I have a loud hiss, not buzz noise now with the JL when I didn't with the clarion. Everything is the same except the radio. The only way to get rid of it is to turn the gain down to like 1/4 on the amp, but then the music wont go loud at all. I know this radio puts out like 4 volts and old was lower. If I disconnect the RCA the noise goes away. I even tried to isolate and run only 1 set RCA to the radio and disconnect all the other amps. Noise still there... My ground is 0/1 gauge right to the battery. I tried 2 different brand rca cables with no change. I know the gain is not a volume control, but I should be able to set it the same. Does the higher 4 volt outputs make a big difference? Here is my setup. I isolated all the audio lines from the power lines also.I'm lost...Do I need a noise suppressor? I was fine with my other radio. One other note. My JL sub amp has NO hiss at all from the sub. Help

You can’t set the gains to the same position with the new HU, as you did with the old HU. The reason is because of that 4v you mention. You need to retune the amps with the new HU.