Quote Originally Posted by MLA View Post
Unless your house battery is a complete stand-alone bank, which it doesnt sound like it as its connected with an ACR, then at the end of the day, all grounds are common and all lead back to the engine block. In most cases, we find the root cause of unwanted noise in boats with dual banks is the head-unit is still on the factory boat harness and draws from the main cranking battery, where as the amps are drawing from the house battery.
You're correct in my set-up. I actually suspected the same thing (head unit being supplied thru factory harness), so I wired the head unit main power to the house battery as well, and there was NO change. I think the amp has issues, and the noise is a tone that's above my 80Hz cutoff now.

Not perfect, but it works and I'm happy with it