This is non-boat related, but my tow vehicle.

Some background. I have replaced the entire stereo system in my 2008 Toyota Tundra. Previously base OEM. I have installed the following major components;

Pioneer AVH-P3400BH- DVD head unit
JL Audio XD700/5-amplifier
Polk Audio MM6501- 6.5 components front doors
Polk Audio MM651 6.6 coaxial rear doors.

I am using aftermarket speaker wiring from amp to speakers, 16 guage.

My problem is that I am getting a high pitch wine or hissing sound through the speakers. First though is alternator whine, but I am not certain. The noise is constant. It does not vary with engine speed. It does not vary with stereo volume. It is there with ignition on/engine off. It does go away with ONLY radio on, ignition off, engine off.

The main power cables do not share the same space as the RCA wires. I have unplugged the RCA wires from the amp, while hearing the noise, and it goes away. I am guessing the noise is from further upstream.

Before I start tearing back into it, What do the audio experts suggest?