Ideas before I rip it apart....

[SmallTruk]

That was something else I thought about too. Everything looks fine with the back cover removed though. I'm honestly stumped, not sure where to go with it right now. I kinda want to insulate the end cap so it can't contact the case in a conductive way and then solder in a wire to the outer connection on the RCA's to the ground and be done with it. But I know there's something wrong and it's gonna bother me no matter if I get it to work with some half ass setup.

[SmallTruk]

Got one issue resolved: the crackling when I'd tap it. After looking it over for the 100th time I just happened to notice a tiny black spot on the top of one of the transformers. I looked at the back cover and there was a tiny hole rubbed through the plastic sheet and was making momentary contact with the transformer when tapped. Glued in a small piece of thin rubber and its fine now.

Still have the high pitch tone coking through the speakers when the RCAs are connected along with both the power and protect lights being on together.

[Cadillac John]

Possibly a dirt signal?

I had a strapped set of amps that the rca's where touching that cause the same noise. Try organizing the wires to see what will happen. I know power cables next to rca's can cause the same thing.

Probably not a lot of help, just some ideas to take in.

[SmallTruk]

Already did that, twice. Lol. I got all the power cable runs on the drivers side, RCAs and speaker wires on the passenger side. I tried connecting a new set of RCAs directly from the HU to the amp and same thing. Everything is the same as it was when I just had the single amp powering the subs and it was fine then. Just with the addition of the 2nd amp I get the noise now.