Amp Making a Siren Noise

[westdoor]

Hey everyone, I've been having a problem with my amp. Before people jump to the conclusion that this is alternator whine, my problem has been happening when the engine isn't on.

Basically what is happening is that I was doing a new install in my car and hooked up my sub and amp and figured i may as well use my old amp (Old Planet Audio P200.4s) and wiring to get my door speakers up to par. I had used this amp previously on some low powered subs and it had always been really good to me.

I used all of the old power/ground wiring, ran new speaker wire, rca's remote. I hooked it up and was fiddling around, seeing how it sounded, and I had it pretty loud. I turned the gain down a bit to play it safe until I got everything tuned and everything went haywire. My speakers freaked out, I'm pretty sure my sub did as well. After I shut the car off and sat there for a second, I turned the car back on and everything seemed normal, but after a little bit of playing I noticed a weird siren sound, like an old air raid siren. Tried new RCA's, tried hooking my phone up directly to the amp with a 3.5mm->RCA adapter and the noise was still there, it kinda came and went. I eventually went back to just having everything hooked up to my head unit.

Any ideas about if my amp is toast, what happened would be appreciated.

The amp is out of my car and the wiring is under the carpet so I probably won't be able to get back out to it soon, but I just wanted to see if anyone ever had experience with this before.

https://youtu.be/o3PaXWWipLo?t=1m2s What the amp sounds like

Pics of the amp

[SnowDrifter]

To verify: The noise isn't coming from the physical amp itself, but rather through the speakers right? Ground loops will do all sorts of funky things. Verify all connections are clean and tight, then ground your RCAs. See google for pics on how to do that as I'm on mobile right now

[westdoor]

I don't have the amp in the car right now, but I'll check that when I get around to it. I tried two different ground locations on the chassis and sanded them down.

And yes, the sound is coming from the speakers. I also noticed that its louder at 0 volume but tends to die down a bit if i turn the volume up 1 notch (out of 50) when the audio is barely audible.