View Full Version : engine noise...why?

10-14-2004, 06:10 PM
i know it's engine noise, because it's only on when the engine is on, and goes up with rpm's. i just installed my amp for my mids/highs, and the engine noise is driving me crazy. i even bought new rca's, but i think the noise got worse. i've tried switching the rca's to both sides of the car (away from power wire), but the noise doesn't even fluctuate. thoughts?

10-14-2004, 06:18 PM
Alternator puts out a lot of ripple current, if your battery is
getting weak or your wires are crappy / crusty / loose the
battery no longer does a good job of flattening the voltage.
Of course if one diode in the rectifier pack goes, this gets
way worse. But that's where I would start. If you took your
stero gear power feed off the battery (like via an ACC-
switched relay) rather than off in-cabin wiring that might
also provide you a quieter source.

But a good piece of equipment should have decent PSRR
and knock all that whine way down for you even if the
supply is a bit lumpy.

You could get a choke and some big caps and try making
your own power supply filter.

10-14-2004, 06:56 PM
honestly, i don't know what you just said, although it sounds helpful. do you think you could clarify what you meant by the acc-switched relay and the power supply filter...

10-14-2004, 07:09 PM
there are SOOOOOOOOO many reasons why you could get engine noise interference in a Car audio system, there isnt any way that someone could really diagnose your problem over the internet.

some of the main causes of this in most apllications are:

-what he ^ just said
-A bad ground(I'd try to find a better ground)
-shitty RCA cables
-Running power or ground wires close to RCA cables or speaker wires.

there are seiously 100's more reasons why this could happen, but I's start there.

10-14-2004, 07:52 PM
well, the amp ground is good, i've already changed it twice, and neither time fixed the noise (i even re-connectored it too). i bought another pair of more expensive rca's, but they made even MORE noise than the cheaper pair i have. i'm a little stumped. it's not the ground, and it's not the rca's or where they are being run. hell, i even hooked up the rca's to the "rear speakers" rca-out on the HU, and got the same noise as i did when i ran the rca's from the "front speakers" output.

while i'm trying to locate the source of the problem, the engine noise isn't going to hurt my speakers, is it? once the music is on, i can't even hear it, so as long as it's not damaging anything, i don't really care if it's there. it's just a minor problem i would rather have solved (even if it must be eventual).

10-14-2004, 08:07 PM
i had an epiphany...

stock speaker wire possibly?

10-14-2004, 11:48 PM
Are you using a good quality amp? I have had cheap amps do the same thing. If you you can try the peripheral P1. It usually knocks out any noise. If you are using a four channel amp then you will need two of them.

10-15-2004, 12:18 AM
i've got 2 amps, and the one running the fronts is a rockford. i found out, over at, that factor HU ground sucks and is probably the problem (hopefully). i'll give it a shot, and maybe that will solve the issue.

10-15-2004, 04:22 AM
pretty much this is how is goes... a car runs of DC power... this is why you have to 'Ground' things to get them to work... it simply connects the system together and completes the 'loop'....

Try eliminating one thing at a time by reconnecting the loop and disconnecting one source at a time. I have some engine noise in my stereo... I always have... even in my last car.. it's not bad at all... kinda sounds like a turbocharger in the rear of the truck more or less.... It's the fact that I am running so many audio devices and most of them are different brands which use different grounds and are all made differently from eachother.

If you think it's your amp in the HU... try grounding your head unit to the same place as your amp and the rest of your system. I think you have a ground loop problem... but like I said before, It could be ANYTHING.

10-15-2004, 07:30 AM
To verify if the noise is entering thru your head unit or amps/wiring do this: Disconnect the RCA inputs to the amps while the system is on, and use a different source of low level audio. For example, use a walkman or ipod with a cable that plugs into the headphone out and has 2 RCA's on the end. If you still have the noise, you'll know that it's not the head unit. You can also do this with a home stereo/dvd/playstation etc.

10-17-2004, 04:04 PM
i actually bought a ground loop isolator and that took the noise out. i didn't ask any questions, and it was only $16.

10-17-2004, 11:25 PM
is THIS ( the one you got?

10-24-2004, 10:34 AM
The first thing you need to do, and this fixes the problem 99% of the time, (also what jimmy blue was saying). Run your preamp wire AWAY from any 12v wire. I run the preamp down the passenger side of the car and the battery (12v and ground) down the driver side. Just make sure the two dont cross. Try this out and let us know if it fixes it ;)

10-24-2004, 12:38 PM
that takes too much time ;)

the isolator completely fixed the problem, and it took about 2 seconds. i bought the one from best buy for $15. the sound quality is still above-par.

10-25-2004, 08:06 PM
Well you can do it right, or you can rig it...the choice is yours :)