Freind has a problem with an engine whine commin through all the speakers which are routed through his amp. He replaced his RCA cables, everything is shielded and in properly. Any thoughts on what the problem may be and how to fix it?

He replaced his RCA cables, everything is shielded and in properly.

I must confess I tend to struggle with comments like this. Unless your equipment is utter rubbish (and of course assuming no components are broken) then it must be a wiring issue so just how 'properly' are the cables done? For example, the RCA's might be well away from the power cable running to the amps, but are they far away from ALL electrical cables in the car? Are the crossovers anywhere near any of the cars looms? Are the amplifier and battery earths the right size and tight etc? We get many cars here that are owner installed and have system noise; usually it's something little like the above mentioned issues.

If you could list the components in the system that would be handy too.;)

cables are run down the opposite side of the car to all the power, just to make sure tho we ran the cables str8 from the H/U through the middle of the car to the amp nand then the prob was gone, put them back along the side channels and the noise was back, so we ripped em out and ran them though the middle again (juz layed across the console n back seat) but this time the noise was still there. he has lower end sony H/U and 2ch kicker 300max 150 rms amp, 2 ch bridged to the woofer or 2 channels to 2 rear 6". when the amp isnt plugged in and the 6's are run off the h/U theres no probs. all the wires are in tightly and we cant see where we could be getting any interferance. Does this mean the amp has kicked it in?

By the way he has had the system running fine since installed (6 months). This has only started happening in the last 2 weeks.

HU RCA tracks could be burnt

cables themselves could have a split in the sheilding.

How can i tell if the HU RCA tracks are burnt?

we replaced the RCA's unless we happended to get another dodgy cable?

I'd suggest that the amp is dodgy. May have some signal input connector problems - specifically, the shield (outside) part of the RCA chassis mount connector to the amp ground.

Often when in a high vibration environment, the solder connection can break. This can be due to bad wiring, loads of vibration from subs, or even just running over really rutted roads.

I'd try and swap in a known good amp, see if that reproduces the problem.

Oh, and another thing, is this amp screwed down directly into the car? I mean like metal screws holding a metal amp body into the metal of the car itself? If so, try isolating any possible earth leakage by screwing down the amp onto a sheet of MDF (or anything else not metal and non-conductive) and then screw that into the car. I've fixed a couple of 'dodgy' amps by doing that.

I'm with Marty on this one - ground loops, engine (alternator) whine and the like can be fixed 99% of the time by good wiring and mounting practices, and good quality cables and connectors.

thnx for the help guys have a fiddles tomorrow n see if i cant put some of your suggestions to good use

That's why I said "assuming all the equipment is okay". Have you got another amp lying around you can test with?