i have a 94 prelude. I have recently installed a sub and amp. when the car is on (but not the engine) it all sounds fine. but when the engine is on, when the volume gets to about halfway there is a very loud high pitched squeeling noise that increases with more volume increase. It does not increase as the engine speed does (at least that I can notice). any advice? i have checked the connections and the power and signal cables are on opposite sides of the car. i do have some of the spare wire kind of grouped up in the trunk, but not very much, maybe 1-2 feet. I cannot figure out what is wrong. should I get a capacitor to hook up to the alternator? should i get some of those "interference reducers" or whatever, that hook up to the wires?

 

Get rid of that 1-2 feet of overlap in your cables and see what happens...

 

You have alt. "whine" it can be caused by a ground loop, or induced.

What is the....

MM&Y of car?
Make and model of amp?
Make and model of HU?
Where/how is the RCA cable run?
How/where is the amp grounded?
How long is the amps ground cable?
What gauge is the amps power and ground cables?
How and to what is the amp mounted?

All the above need to be answered. 94

 

Alternator whine that doesn't increase with RPM? Doesn't sound like it to me. Problem starts at halfway volume and up. Sounds like a bad amp to me.

 

It could be a lot of things. How long is your ground? Is it a good ground? Did you run a ground loop? Have you tried a different set of rca's? Aftermarket or stock radio? **** sometimes i've even seen it be a bad set of plugs, random i know, engine noise is kind of a trial and error thing. If you have it just try replacing one thing and go down the list till you find out what was the problem

 

I'm going to agree with both fcm and suspendedhatch

Not enough information provided to debug.
It could be a power supply on its way out.
Or you could have a bad ground somewhere.

 

Hey everyone thanks for all the help. I figured it out. I actually had my rear speakers unplugged and the wires were dangling freely.