Stereo Problem

Ok I know that one of my problems is that I have cheap products but hear me out.
I have a pioneer DEH-2800 HU
a Lightning Audio S4.600 4 channel amp.
I have the acc and the ground wire for the HU going to the factory wiring and the constant power going directly to batt #2 with a fuse. I am running 8 gauge power and ground wire directly from the second battery to the amp. I know I should go bigger but like I said it worked before. I run two batteries that are on a Stinger isolator. I never had a problem up until 7-4-06. I had an RCA cable go bad on me so I had to switch it out. The problem was that due to where I had to mount the amp I had to pull the amp to change out the cable. After that I have been getting some serious feedback. Whenever the volume is at 0 I get a heartbeat noise (Engine off). If I turn up the volume loud then back to 0 it goes away. If I try to start the motor I first get the fuel pump noise followed by the starter really loud. I no longer get a soft turn on or off from the amp. I am confident that the amp is not the issue due to the fact that I have tried a swap out with an RF 401S amp and it performed the same way. I have tried moving both power and ground wires on both the amp and the head unit with no avail. I wouldn't be as upset if it did not work fine for the previous year. The power wires are separated from the speaker wires. I am pulling out what little hair I have. I do know a little about stereo, no expert by any means, but a little. Any suggestions would be greatly appreciated.

Cory

Power too close to your RCA's. most likely.
stay more than 12" apart and only cross them at a 90 degree angle. Try another pair of RCA's temporarily from deck to amp it should go away. (not tucked away but over the seats or what ever) to stay away from the battery cables. they may be in the same path as your old ones but, the old ones may have had some shielding your new ones don't have.

Cory,

What happened to the RCA wire? Did it melt? Sounds to me like you have a pretty serious ground loop.

If I understand correctly you are wiring your head unit to one battery and your amp to another? If this is the case your RCA's might be trying to carry the ground current to balance the batteries. In addition to ignition noise you will likely burn up your RCA's again. The solution would be to wire everything but your deck's turn on lead to the same set of battery. Best case scenario you should pull the yellow and black, power and ground to the deck, off the same source as your amp. If you wish to maintain the existing switching you can probably leave the red wire to the deck where it is now, but not the black.

Well the bad RCA was not the result of it frying but rather the end fell off (cheapo). I have tried every configuration imaginable to get the noise to go away but after talking with a friend who said he had a similar problem in his truck I think it’s the deck. He said he was getting all sorts of feedback then swapped out the deck and it was gone. It was a pioneer deck too. If I disconnect the RCA cables the noise goes away both from the engine as well as the on/off noise. If I use the $40 RCA cable's it does the same (cables out over the seat). Is there any rationality to this? I was originally starting to think this but my friends comment seems to add fuel to the fire. Your thoughts? By the way the deck is only 14 months old

Well here is the update. I swapped out the deck and the problem went away. I decided to go with the DEH-P4800MP. I like it alot better. I guess there is one way to get an upgrade.
Along the lines though, any idea why this may have happened? Could it be that the RCA cables were trying to carry the ground load from having the amp and the HU on seperated batteries?