noise introduced through rca wires

[BigWizzleFoShiz]

My stereo is a pioneer, its an older model mp3/cd player. And I first installed it into my jeep cherokee 1987.and I got an amp and hooked it up, at first there was no noise and after a while a constant thumping noise was reverberating through my subs. i got a noise filter this seemed to help the problem but just made the noise quieter and also my music coming through them. Later I got a Honda accord, and it had the same problem, though a different noise.

(it sounds like the engine is being amplified through the subs. but it does not come through the HU amp tho). Anyways I got tired of the noise so I tried using my girls HU, bad idea same thing happened to it. Now hers does it, Which i also installed a rca noise filter. helps but doesnt fix it. The main reason why i am having problems is because. the sound coming from the HU is not as loud as it used to be. speakers used to sound powerful but now sound like their signal is not strong enough even though it is still pretty loud.

if someone could please help i have been having this problem for about a year now.

[Hautewheeler]

sometimes amps go bad..

have you tried using a different amp? - you said that you have used different vehicles, and a different head unit..

I did have an old sony hu that did the same thing until I blew it up with some firecrackers.

[BigWizzleFoShiz]

yeah its not the amp, if i deisconnect the rca's it goes away even hooked upo house stereo rcs no problem

[Hautewheeler]

wow this is deja vu..

the amp has an internal noise filter, because all electrical systems generate electrical "noise".

when that goes bad, it "amplifies" the noise that is coming from the engine's electrical system, rather than cleaning it up.

try this.. make sure that your rca's are not running right alongside the power wires for the amp. this will cause noise distortion.

make sure that your big three are solid
battery negative to chassis ground
engine to chassis
and battery positive to amplifier

sometimes noise is cause by a bad ground here, and typically these wires are cheap little ground straps made from flat braided wire.

make sure you are using decent quality rca's and not magnavox. cheap rca's go bad often, but they won't "cause" noise, just transfer it.

might be easier just to try a different amp first, and see if you still notice the sound.. either way, take care of the big three.

[Ranger SVO]

Noise is so difficult to locate and fix without having the car here to look at. Everyone always blames the ground, but this is not always the case. To reduce noise manufactures usually float the shields above ground, and that is where the problem starts. Different manufactures float the ground differently.

I was recently reminded of that when I changed an amp in my truck. My truck was completely noise free and then I replaced an amp, using the same existing power wire, the same existing grounds, the same RCA's, in fact the amp that was replaced was a Kenwood and the new amp was a Kenwood. All of a sudden I have an RPM gauge that I could here through my speakers. And it was loud.

The problem was not a bad ground, it was a potential difference in the grounds. Both the radio and the amp have grounds to the vehicle chassis. Filters don't fix problems they mask them.

Now in my case it was as simple as running an 18 ga wire from the chassis of the radio to the chassis of the amp, the noise is completely gone.

To fix noise you will need a DVM and a basic idea of what to look for. I do all my measurements with the negative lead of the DVM hooked to the batt neg. This way all my measurements are with respect to a single ground. Now look for the difference, thats your noise problem.

In most cases its easy to find, but I have run into an interesting case once in a great while. Lose any noise filters while you are looking for the problem.

Of course always do the obvious first, make sure the grounds are solid, if the radio is using a factory ground, cut it and go to the chassis if the car. Disconnect the antenna to make sure the radio is not grounding through it (antennas make terrible grounds).

Throttletune posted a method recently on a quick way to check grounds, with every thing turned on set the DVM to volts (neg lead attached to the batt neg, everything with respect to battery) and check to see if there is any voltage on the amps negative lead. I don't recall what he said was acceptable, but if you have a 1/2-volt its too much.

At this point properly diagnosing the problem will yeild a solution. I wish I could be more help

[The Viking]

Glad to see you back in action around here Ranger!

Ya, that is one way to start the process....... and a good one at that.

If ya wanna try other things, i will also help out the process too a point, like was said, without the cat actually being in front of me in my shop, its hard to trace these things dowm at times.

Try some of these basic procedures...


If the noise goes away at any one of these let us know...


Disconnect RCA's from radio

Disconnect RCA;s from amp

Unplug antena lead

Noise gets worse when you turn on the lights and wipers and blower at the same time

Thats a starting point , let us know what you find......but if you have and know how to use a DVM, do what Ranger said also........Need a baseline to go from on these things....

[BigWizzleFoShiz]

Ok,

before i went to work today i ran wires directly from the battery to my stereo, and had no luck. i then disconnected the rca noise filter (it is a set of grounded rca's) and the noise is obviously not the car engine it makes the noise when the car is turned off. but it sounds like a car engine. the noise goes away when i disconnect the rca wires from the hu or the amp, tried both ways. the antenna is allready disconnected i did this a while back because i thought it helped somewhat? and the noise doesnt get worse with the wipers/blower on.

the noise is somewhat tolerable to a point that i wont stop using it. it pounds really hard . the bass probably hits as hard as it would but not as clean. by the way i have a pioneer deck, kenwood 12's, and a sony 1200 watt xplod, in a poreted box with the ports blocked with fabric

i was thinking about a sony deck - go or no?


i took the noise filter off for the time being, it didnt really help just made the signal to the amp weaker.

[Ranger SVO]

Originally Posted by BigWizzleFoShiz

Ok,
the noise is obviously not the car engine it makes the noise when the car is turned off. but it sounds like a car engine. the noise goes away when i disconnect the rca wires from the hu or the amp,

I went back and read your first post, and saw no mention of the noise problem with the engine off.

What you are describing is an amp problem. Without hearing the noise, I am guessing the amp is going into oscillation (don't know if its the right term), if so replace the amp.

I don't like throwing money at a problem so have a shop check the amp. Let us know whats up, but I suspect the amp.

[The Viking]

ditto............

[BigWizzleFoShiz]

well, i saw the sony decks on sale 35% off and grabbed me the nicest one. works fine now no noise whatsoever and i have a 3rd rca for my subs . just thought i would let you guys know because i had you stumped. pioneer car stereos just dont work for me, maybe premier but i cant spend any more money on em.