Slight Alt. whine & speaker "pop"

[UNHCLL]

I am getting a very slight amount of alternator whine through my speakers after installing a new 4-channel amp. I also get a very slight "pop" as a roll in and out of the throttle, which I believe is tied to the alternator generating power.

The amp is currently grounded directly to the negative battery terminal. Is this the likely cause of my issues?

All RCA's and speaker wires are run down the centerline of the car, and not next to the large positive battery cable that runs the length of the right side of the car.

Thanks,
Chris

[Schnitzer318is]

What brand amplifier is it? Are the RCA's shielded at all?

Battery terminal grounding should be fine... always worked for me with no pop or whine anyway. Did you run a return ground? I almost never have to do this, but I've heard it can help in some cases.

Have pics of the install & wiring... might be able to see a problem?

[StereoInstaller1]

As ususal, I would like exact brand names and model numbers of everything...locations and pictures of grounding points, too...but if you ran normal "car audio" grade RCAs with some form of shielding (they should be run up the left side, BTW, not the center) you should have no pops of any kind.

You may have a bad amp.

[UNHCLL]

Rockford Fosgate Twisted 16' RCA's (3 sets)
Boston Acoustics GT-50 5 channel Amp
RF 60 Amp fused power lead (4 gauge)
RF Ground wire (4 gauge)

Power lead comes direct off the positive battery terminal.
Negative goes direct to the terminal on top of the battery, not the grounding point on the outside of the chassis/fender wall.


No easy photos of wiring, but here is where the amp is mounted... to give you an idea of the wiring run for the power & ground leads. They run right along the main battery cable lines that are behind the carpeting panel.




Also keep in mind on an S14 powered car, the alternator does NOT produce charging power at idle. The pop only occurs during on/off throttle application, and is less subtle that hooking up a 9V to the speaker leads.

If I turn the key on, and turn on the stereo, I get ZERO whine, and no "pop".

I am not familiar with what a "Return Ground" is. Could you explain this further?

[dashboardmonkey]

Return ground is a small ground wire run from the ground on your deck to the ground on your amp. It is used to equalize ground resistance (I think) between the two components.

[UNHCLL]

the whine is worse when the headlights are on.

[Schnitzer318is]

the whine is worse when the headlights are on.

The harder your alternator has to work, the worse the whine will be... Does the whine go up and down with throttle?

Did you shoot sheet metal screws through the firewall to mount the amp? Or is it mounted to a board behind the trunk liner?

I agree with Luke and always run RCA's down the left side of the car (on BMW's anyway).

Sounds like you might have to deal with the "pop" in your application due to the charging system of the s14? Sucks that it's everytime on throttle from idle.

[dashboardmonkey]

the whine is worse when the headlights are on.

The whine is worse because the alt. is working harder. Run a return ground like I explained above. If that doesn't work run a wire from the small ground to the amp to the ground on your RCA's. Or if you tried the first option don't remove it, jump it to the RCA ground (outside terminal of RCA cable end) you will have to solder it on, make sure to rough it up a little or it won't stick.

[StereoInstaller1]

I believe the Fosgate RCAs are directional.

Laugh all you want, but here is the real skinny: they only ground (signal ground, not chassis) at one end...I can't remember which end, but only one...and the damn things have tiny fucking arrows or use the lettering to indicate signal path.

You might wanna grab a different set of RCAs to run externally, just to check.

Terrific amp, BTW.

Luke

[UNHCLL]

The harder your alternator has to work, the worse the whine will be... Does the whine go up and down with throttle?

Did you shoot sheet metal screws through the firewall to mount the amp? Or is it mounted to a board behind the trunk liner?

I agree with Luke and always run RCA's down the left side of the car (on BMW's anyway).

Sounds like you might have to deal with the "pop" in your application due to the charging system of the s14? Sucks that it's everytime on throttle from idle.

Yes, whine goes up in pitch (not volume) as engine speed increases.
Amp is mounted direct to a carpeted panel of Maple(?), which is subsequently screwed direct to the firewall. Amp is NOT connected directly to the chassis metal in any way.

I have friends with very very expensive audio systems in their e30 M3's, and they don't suffer the 'pop', so I know it can be cured. I still suspect my grounding method or location is not sufficient....

The whine is worse because the alt. is working harder. Run a return ground like I explained above. If that doesn't work run a wire from the small ground to the amp to the ground on your RCA's. Or if you tried the first option don't remove it, jump it to the RCA ground (outside terminal of RCA cable end) you will have to solder it on, make sure to rough it up a little or it won't stick.

So, you're suggesting I run a ground from the Headunit Ground, to the ground terminal on the amp, which also has it's main ground going to a location on the battery/chassis?

I believe the Fosgate RCAs are directional.

Laugh all you want, but here is the real skinny: they only ground (signal ground, not chassis) at one end...I can't remember which end, but only one...and the damn things have tiny fucking arrows or use the lettering to indicate signal path.

You might wanna grab a different set of RCAs to run externally, just to check.

Terrific amp, BTW.

Luke

Curious... I will have to take off the inspection panel on the amp and climb into the trunk and inspect the cables. That would be a real bummer if the cables were directional and I failed to notice this.

Once the whine is resolved, I'll need new speakers. The amp has proven the OE speakers are just sub-par. They were acceptable when being run off my headunit, but no longer.



Can you guys explain why you suggest running all the cables up the left side of the car? I've always been instructed to run signal wires as far away from large bundles of wiring as possible. Obviously the right side is out due to the positive battery lead, and the left side has the majority of the body harness in it... hence why I always wired up the center. This is the first time I've had this issue.

Thanks for all the help guys, I'll dive into this over the weekend and see what I can find.

[dashboardmonkey]

So, you're suggesting I run a ground from the Headunit Ground, to the ground terminal on the amp, which also has it's main ground going to a location on the battery/chassis?

yes, so when you are done you have 2 ground wires on your amp (main big one and one small one) This will make the deck and amp have the same level of ground.

[jakeb]

I have this same issue in my e30. No s14 though. I have a m50.

I will also try the secondary ground. My amp is mounted directly to the metal firewall in the trunk. Does this matter?

[StereoInstaller1]

I have this same issue in my e30. No s14 though. I have a m50.

I will also try the secondary ground. My amp is mounted directly to the metal firewall in the trunk. Does this matter?

Grab a voltmeter, set it to ohms...check resistance between the chassis ground and the ground terminal on your amp (unmounted, of course) and if you have continuity, it matters.

While your amp is not mounted, fire up yuor car and listen!

[Schnitzer318is]

Luke, I did not know that about the rockford's. Will have to keep an eye out for that in the future.

As for the problem at hand... I was just guessing about the "pop"... I'm glad to hear that it can be cured since other m3'ers are running without it. Have you tested another amp on the wiring?

[StereoInstaller1]

Yeah, Fosgate pretty much started that shit back in the mid 90's.