The RCA's and speaker wires run on the driver's side area while the power and grounding is located on the right hand side. I had all speakers rewired to connect to the amps. I am currently getting lots of interference on my AM stations to the point where I don't even listen to AM anymore. The interference happens all the time and there is no difference whether I am accelerating or not. The interference varies depending on which area I'm at - just as if the AM signal is weak. There is an option on the CDA-7875 receiver for NORMAL (better reception) or Hi-Fi (better quality). I set it to NORMAL as a factory default with no improvement.
I had everything installed at a retail store, and went to three stores and they all could not fix it. I had a Bose factory radio in it before and never got any interference. I previously had an Alpine CDA-7873 with just the 4-channel MTX mounted under the driver's side seat with no problem, at least as far as I can remember. I had it for 20 days before I upgraded it to the CDA-7875 and added the Alpine MRV 757 amp and the two JL103 subs (I also got a power kit).
The 4-guage power wire runs from the battery to the power splitter, which expands to four power connectors. I am currently using two of the four for my 4- and 2-channel amps. The reason for the interference the technicians gave to me is that my antenna that came with the Integra is not compatible with these third-party brands (as opposed to using the factory radio). They suggest that I upgrade my antenna to a more powerful external type. (The only reason why I don't think it's the antenna is because the reception was ok when I had the CDA-7873 before I added all the other items: MRV757 amp, woofer, moving the MTX 4-channel to the back seat from the bottom of the driver side seat, and using the power wiring kit.)
They tested the grounding and it was not the problem. They tested it to the point of checking the grounding wire itself for physical damage from the receiver going back to the place where it is grounded. They also tested different third party receivers with similar interference coming from the AM stations. The only physical damage I found was a hole drilled through the grounding that runs from the MRV-757 amp to the metal body of the car. The installer accidentally drilled through the grounding when he was attaching the screw for the amp against the back seat. He said it does not really affect the AM problem I am having so he just taped it with electric tape. He also accidentally drilled through the power cable running from the power splitter to one of the amps. Actually he blew the power fuse of the kit because of that. Anyway, he replaced the power cable that runs from the power splitter (where the main 4-guage wire was being split) to the amp - 6 gauge. Anyway, I am out of solutions and it's a bit of a disappointment spending more than $2,000 for my car system when I can't listen to the Dodgers or Lakers because my AM station is completely too noisy. Hope anyone there can help.Thanks,Frank Ramos
First off, I'd be a little skeptical of an installer who drills through both a ground wire and a live power wire. He may just be having a bad day, but this is a bit too scary for me.
The only significant changes you made were the replacement of the head unit and the addition of the Alpine amplifier. If you would have stated that you were using an ancient amplifier you found in the attic, I might be tempted to suspect it. In the early days of DC-to-DC converter amplifiers, one common problem was excess radio frequency radiation from the power supply stage. This caused problems for AM reception, and like your situation, did not vary with engine speed as normal radiated noise would. To confirm that the amplifier is not at fault, simply pull its fuse to disable it, and note if there is any improvement to the AM reception. I'll bet there is no change.