I got the tech working for 5 hours on the vehicle right now lol. When he showed up and saw the alternator and rpm make the whine, he said the new alternator is bad and I need to replace it. He said he had cases when the brand new oem alternator was making noise, and aftermarket rebuilt alternator fixed the issue. I said ok, how are you testing it to condemn the alternator lol? He doesn't have an oscilloscope. Like for real, both alternators bad and even with Newmar amp filter??
He tried a different amp, different speaker, all the same results.
Thankfully there's a loud static noise when the ignition is on, without starting the car. So that rules out the alternator...

Basically it looks like there's some kind of a short somewhere. We tried powering the system without turning key to on, and it doesn't make any sound.
There's some short somewhere for sure.
We tested resistance between headunit and metal bar under the dash, it's 0.
Then it I turn the key to "ON", that resistance jumps to 30 omnhs. Gotta find that short.
Some component that is activated by the ignition is grounding onto the vehicle ground. With higher rpm more amperage gets sent to the ground, and the ground loop gets worse.
That's my theory for now. Gotta look for that short with ignition on

When I turn the ignition is