Should Direct Ground to RCA Cause Noise?

[lpm]

Hi - I am chasing an alternator whine on my newly installed system.

If I unplug my RCAs, the whine goes away, but touching the outer RCA directly to a jumper cable on the negative battery post brings back the whine with RPM.

I have replicated the issue with 3 sets of shielded RCAs and my amp is also grounded directly to the negative battery post as well.

Should directly grounding an RCA cause whine, or is there a problem with my amp?

Thanks!

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[lpm]

edited out comment

 

[Buck 5,000+ posts]

Is your amp screwed into the metal of your car via the feet?

 

[Buck 5,000+ posts]

Sounds more like an alt issue or noisy alt. Your alt converts ac to dc, in a way, and it sounds like you're hearing it through your 12v system possibly.

 

[lpm]

Is your amp screwed into the metal of your car via the feet?

Thanks for the reply.

No, my amp is just velcroed to my trunk carpet.

 

[lpm]

Sounds more like an alt issue or noisy alt. Your alt converts ac to dc, in a way, and it sounds like you're hearing it through your 12v system possibly.

This seems like a strong possibility.

1. If I run my factory amplifier off of the amplified headunit outputs, it sounds perfectly clear.
2. If I feed my aftermarket amplifier with the headunit RCAs I get a whine.
3. The whine increases with amplifier gain, but not with headunit volume.
4. It goes away when my rca's are unplugged and not touching anything.

This seems like some sort of ground reference voltage difference to me, a "ground loop".

What I'm confused about is that if I connect the RCA ground and the amp ground both to the negative battery cable, there should be no "loop" causing any ground reference voltage difference.

Maybe I will take a multimeter to all the grounds around the car to try to find any loops, but everyone says you shouldn't have to use any filters if your install is done well.

 

[Buck 5,000+ posts]

This seems like a strong possibility.

1. If I run my factory amplifier off of the amplified headunit outputs, it sounds perfectly clear.
2. If I feed my aftermarket amplifier with the headunit RCAs I get a whine.
3. The whine increases with amplifier gain, but not with headunit volume.
4. It goes away when my rca's are unplugged and not touching anything.

This seems like some sort of ground reference voltage difference to me, a "ground loop".

What I'm confused about is that if I connect the RCA ground and the amp ground both to the negative battery cable, there should be no "loop" causing any ground reference voltage difference.

Maybe I will take a multimeter to all the grounds around the car to try to find any loops, but everyone says you shouldn't have to use any filters if your install is done well.

Well there would be a loop because the alt is still inside of that loop that you made. If you don't start the vehicle, does the amp still whine?

 

[Buck 5,000+ posts]

This seems like a strong possibility.

1. If I run my factory amplifier off of the amplified headunit outputs, it sounds perfectly clear.
2. If I feed my aftermarket amplifier with the headunit RCAs I get a whine.
3. The whine increases with amplifier gain, but not with headunit volume.
4. It goes away when my rca's are unplugged and not touching anything.

This seems like some sort of ground reference voltage difference to me, a "ground loop".

What I'm confused about is that if I connect the RCA ground and the amp ground both to the negative battery cable, there should be no "loop" causing any ground reference voltage difference.

Maybe I will take a multimeter to all the grounds around the car to try to find any loops, but everyone says you shouldn't have to use any filters if your install is done well.

After you said this though, I wonder if there's an amp problem. Man that's kind of weird. But seriously play it with the engine off and see if it whines. Also, do you have sheilded RCA's? Are your RCA's ran right beside your power wires?