ground noise engine dependent....?

[GINA2MR2]

mods.
the guy before me had the rear pillar speakers and the door speakers run through a aftermarket amp. i also have a 10'' Cadillac sub running through a separate amp. i dont have tweeters.
the head unit is a sony ... new.


problem ..
i have a buzzing noise coming through my speakers.
it revs when the engine revs
i know its a ground but...

ive checked all the speaker connections and the original speaker amp has been replaced. the sub amp works (ive tested it in another car) ive checked the battery ground, and both the amp grounds. the head unit ground is good.
wiggling the connections dosent change the sound. the alternator has been replaced but the buzzing has been there before it was replaced.

anything ive missed.. ?

[F0Bman]

Yes, its does affect it. The alternator can be a source of noise from the inverter on there.

[GINA2MR2]

but i replaced it .. and the noise was happening when the old one was there. .

[Mista 2]

there are noise filters out there for your head unit. i know Aerpro (TDJ) do make them but i dont know if they are avalible outside australia.

[GINA2MR2]

theres one on there.. po...

anything else?
like i said tried everything..

[Bak@EMSPowered]

if you need a noise filter: 10A Noise Filter 10A Noise Filter [] - $10.99 : EMSPowered, High Quality, Great Service, Low Prices

But I say check your grounds first from the headunit and/or amplifier and also make sure your RCA cables are not passing by anything with high voltage.

[Mister2.2]

Grounds should be connected in one spot IRC. Check your engine grounds as well.

[DenverMR2]

Check that all wires that pass a signal so rca's and wires from the amp to the speaker shouldn't be in the vicinity of high voltage wires.

[GINA2MR2]

the rca arent running by HVW but i will check the engine grounds.. again.. the nosie makes driving the car unenjoyable

[Luni]

That kind of noise is due to a ground loop.

First you need to figure out where the ground loop is coming from. Most likely its coming from the head unit through the RCAs.

It could happen many ways. Common ground loop point is the subwoofer amp not adequately grounded to handle the job, so it naturally wants to ground back through the system through the next closest point. That happens to be the headunit. Since the RCAs are all tied into the same ground point on the head unit board, the loop will then go out through the front and rear channels then be amplified by the midrange/tweet amp you have.

So, if doing the headunit chassis ground doesnt fix it, disconnect the RCA leads from the subwoofer amplifier. If that doesnt fix it, then disconnect the RCA leads from the noise based amplifier. If the noise is gone at that point, youve isolated it to either something between the headunit and noise amp, OR its coming from the headunit itself. To test, get another set of RCAs, run it overland, not touching anything, to the amp itself, and see if you still get the noise. If its gone, its either your RCAs, or its the path they run. If its still there, its in your headunit.

Theres a chance the amplifier itself could be inducing the ground loop at this point, but not likely. You can test that as well by adding a amplifier chassis ground somewhere from the amp to the chasis of the car (most likely this will do nothing because your amp is probably screwed into the chassis of the car already)

Another thing that can be done to help is to connect all your grounds together in a circuit. Ground your deck to a point on the chassis, and then run a higher gauge ground back to the amps and tie into where they both ground as well.

Ground loops can be hard to trace but theres just a few ideas to help you find yours.

Im sure some others will chime in with what has worked for them.

I will add one more thing. If you have power steering, its really hard to completely eliminate all ground noise as the PS system has a high current draw and if youre running wires through the frunk into the cabin, they could potentially pick up the noise. So keep that in mind if you have PS.

Ive done installs into PS equipped cars, and while they never had any inductive ground noise like the whirly whine sound that increases with engine RPM, they did have a slight clicking at no volume. It wasnt even noticeable with volume applied, so it wasnt a big deal. I have never truly been able to eliminate all ground noise associated from a PS car, however Ive never upgraded the "big 3" on an MR2, nor did I add an extra ground on the PS electronic pump either.

[MANDALAY]

MY OPINION.
1st check suspect amp. Make sure ground wire is bolted down to bare metal.
2nd diconnect RCA's.
3rd use use shorted RCA's on all inputs, that is join the + and - .
Start the car , rev it , if whine is present. THROW AWAY THE AMP. The amp is cheap and has a poorly designed power supply.
This is however rarely the case but it can exist.
NEXT.
If there is no whine reconnect the RCA's.
4th Pull the head unit out of the dash. Make sure it isnt touching the car. Disconnect the negative and both positives ( one is the acc ) and power it up with another spare 12 volt battery. ( This mimicks an isolated power supply , there is no reference to the chassis of the car )
Since we find the amp is ok and the head unit power this way there should be no whine.
Try it and rev the car.
Is there whine ?
No ? Reconnect the - and + to the car again.
Try again . Is there whine ?
No , problem fixed.
Yes , buy a isolated power supply for the head unit.
If there is whine with the head unit powered by a separate battery, noise is being induced on the RCA's . Use twisted pair. Question how high is the gain set.

[GINA2MR2]

i will do that.. the amp is new though i threw away the old one and the sound continues