28 replies to this topic

[Adam Franke]

So here's my problem. My subwoofer is picking up engine noise (as you may have guessed from the title) and I don't know how to fix it. I checked over all of the RCA cable and none of it is stripped. The RCA and the Remote are run down the right side of the car together and the power is run down the left. I looked at the connections for the power and the ground, and for some reason I think the ground may be causing the problem, but I don't know how to fix it. I also noticed that when the engine is off, there is a very quiet hum coming from the sub. As soon as the engine turns over, it turns into a roar and then the roar is variable with the engine speed. Any help would be greatly appreciated, although I won't be able to work on it until Thanksgiving after 7PM tonight.

[josh_S70GLT]

You most likely need a ground loop isolator, which you can get off ebay or at your local RadioShack.

[PyROZen]

try moving your ground to a different spot. if that doesn't work, maybe try a ground loop isolator, or maybe your RCA outputs on the HU are bad. just my 2 cents

[potroast]

try unplugging the rca's with the engine running. Can you determine whether the noise is introduced from the power wire, or the signal wire?

[Adam Franke]

Yeah, there are 2 RCA and 1 Subwoofer outputs on the back and it makes the sound no matter which set they're in. Where would I put the isolator? Between the head and the RCA, or the RCA and the amp? I'll probobly go out and buy one in a few minutes here.

[potroast]

If it makes noise even when not connected to the RCAs then an isolator will not do anything.

If this is the case, the noise is being introduced on the power-side.

[Adam Franke]

I bought an isolator, put it in between the head and the RCA cables and it got rid of the noise, however it greatly reduced the bass. There's almost none now. I'd rather have the bass with the hum because when the bass is going, you can't hear the buzz anyways. Any way to get around this? Do I need to tune the HU or the amp to fix this, or is it a problem inherent with all GLI's?

[prasamin]

if your ground is twd the front of the car, change it twd the back...i put my ground under the back seat which lifts up.....thw whole car is grounded, so putting it on any unpainted metal could do it....far away from the engine bay may help

[Adam Franke]

If you mean the ground on the amp then it's already in the trunk.

[BenW]

you may have a shitty ground on the head unit. I ran a wire from the HU ground to the HU chassis and it shut my engine noise up.

[Bing_0]

if you are hearing a humm coming from the subs even whent the engine is off, it usually means your amp is staying ON even when the car is off, where do you have the remtoe wire hooked up?

though your engine whine may be a different problem all togehter, basically, my rules against engine noise is:

quality amps
ground wire as short as possible and of the same guage as the power wire, gorunded solidly to a structural part of the car and wher eht epaint was saned away
power cable and signal cable as far apart as possible.

b

[Adam Franke]

if you are hearing a humm coming from the subs even whent the engine is off, it usually means your amp is staying ON even when the car is off, where do you have the remtoe wire hooked up?

though your engine whine may be a different problem all togehter, basically, my rules against engine noise is:

quality amps
ground wire as short as possible and of the same guage as the power wire, gorunded solidly to a structural part of the car and wher eht epaint was saned away
power cable and signal cable as far apart as possible.

b

The remote runs from the head unit down the passenger side with the RCA cables to the amp. The amp isn't exactly crap, it's a brand new Alpine amp, the ground could be shorter (I'll do that asap) and it is connected to a part that was sanded away. The power cable runs down the drivers side, so it's about as far away as it can get. But yeah, there is a hum when the engine is off, but the key is in position II, and then it gets real loud when the engine is turned on. When the car is completely off, there is no hum at all.

[Bing_0]

so as soon as the ignition is turned on, there is a hum? and this is the hum that gets louder when the engine is on? i have heard that before, and it was a bad inpiut section on an amp, al;pine is a quality piece for sure, but did you try perhaps swapping in another amp real quick to see?

b

[Adam Franke]

Another amp or head unit? I had a suspicion that the RCAs were bad because they seem to cut out randomly at times. Any way to replace that? Just gimmie part names and numbers and I can get it done.

[bogelo]

2 possibilities:
1. You get bad ground.
2. Your input/output signal cables are near/intefering with power cables.

5 Solutions:
1. Always solder your ground for best grounding (the closer is the grounding to the battery, the better). Also don't share the ground with anything else.
2. Separate the input/output cables (such as: RCA cables, speaker cables) with the power cables (don't let them run together in line).
3. buy twisted-pair RCA cables(try monster cable Interlink® 301XLN)
4. buy special "balanced" input cables from your amp' manufacturer, if any (I know that zapco and phoenix gold have these special cables to protect the input signals from any interference)

Usually if you fixed all of the above you don't need the following (if you still have problems, check your amplifier or your car's electrical):
5. buy a ground-loop isolator but I don't think you'll get good sound.

Edited by bogelo, 06 October 2004 - 06:54 AM.

[wattsat]

One way that I use to diagnose if there is a problem with the HU is this.

Disconnect the RCA cables from the HU. Hook up a Home CD / DVD player to your Amp. Turn the Gains on your amp all the way down. Turn on the CD Player and play a CD. Disconnect the Remote wire and jumper it the the 12V+ on your amp to turn the amp on.

If the Noise is still there then it is probably a Ground wire problem or your amp is bad and needs to be returned / serviced

If no Noise is present then you know there is either a problem with your HU or RCA Cables. Next step will be to unhook the RCA's from the back of your HU and plug them into the Home CD Player. If no Noise is present then your Amp Grounds and RCA connections are all Ok and the problem is with your HU or the HU Ground.

Remember, always start at the source with the least number of unknown variables as possible. As the test returns desired results increase the number of variables one at a time until the problem returns.

[Bing_0]

another good way to test anything is with a muting plug,

A muting plug is simply an RCA plug with the two conductors shorted together. you can do this with a pig tail, by splicing the wiring with a crimp. Soldering the pins together is better.

if you plug this muting rca into anything and the noise goes away, move on to the next component so on and so forth...

b

[Adam Franke]

So basically it's a single RCA with two male ends? Where would I plug that in?

[calvin]

You want all your grounds to be in one location ... by putting them elsewhere is how a ground loop is created

Balanced cables arent to stop noise.. they are a impedance balanced set of cables to setup a 'balanced' input level from your HU to your amplifier

Edited by calvin, 07 October 2004 - 12:05 PM.