# Whining from speakers, not alternator whine



## Mast0rMason_ (Oct 14, 2020)

I have a strange noise coming from my speakers from my amp, it's a Vibe A3 4 channel. After about 5 mins of normal listening it will start to make a whining noise around 4khz (guesstimate using a tone generator on my phone). The volume if the HU doesn't effect the volume of the noise nor does the gain it's just constant pitch and volume. Although throwing on the hazards effects it and electric windows. The fans, headlights or anything else doesnt. I've got door speakers at 2 ohms on channel 1 and 2 and a sub wired to 4 ohm on channel 3 and 4 bridged. Pulling out the RCA cables doesn't cause the whine to disappear. If I pull out channel 4 the sub will start to whine louder as before it's not very loud at all. Seems strange that even pulling out the RCA cables it still makes this noise so it cant be interference with the cables either.

If I turn the head unit off and on it will take another 3-5 mins or so to come back so it cant be heat related I dont think

Does anyone have any ideas what it could be? Could it be a ground loop within the amp? How would I go about diagnosing it?

Thank you


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## Holmz (Jul 12, 2017)

If you had a spare battery, it may be possible to hook that up and and see if the noise goes away...?
But cruising around with a battery on the floor is not a great plan.

It seems that it is either coming in through the power, or it's internal.


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## Mast0rMason_ (Oct 14, 2020)

Unfortunately I dont have a spare one 😞


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## Holmz (Jul 12, 2017)

Sometimes a loose stray speaker wire strand can do those things.


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## NIFTY550 (Aug 10, 2020)

Sounds like an issue with the amp if it's making noise with no input connected. Bad filter or power supply problem.


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## Mast0rMason_ (Oct 14, 2020)

Slight update, had my dad run the amp at his work as he has a power supply for it there and no noise. So the only thing I can assume is interference from the engine loom or fuse box going into the power cable? Could explain why the noise flickers when I throw on the hazards. 

Can the power cable insulation just be bad?


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## Holmz (Jul 12, 2017)

Mast0rMason_ said:


> Slight update, had my dad run the amp at his work as he has a power supply for it there and no noise. So the only thing I can assume is interference from the engine loom or fuse box going into the power cable? Could explain why the noise flickers when I throw on the hazards.
> 
> Can the power cable insulation just be bad?


No.

It is most likely a ground loop problem.
Insulation is for electrical fields, and not magnetic fields.


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## Mast0rMason_ (Oct 14, 2020)

Holmz said:


> No.
> 
> It is most likely a ground loop problem.
> Insulation is for electrical fields, and not magnetic fields.


Where could the ground loop be then? Because the amp isnt making the noise at my dads work when hes running it externally? I've redone the grounds on the car. Unless I add another wire from.the chassis to the battery?


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## Mast0rMason_ (Oct 14, 2020)




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## Holmz (Jul 12, 2017)

Mast0rMason_ said:


> Where could the ground loop be then? Because the amp isnt making the noise at my dads work when hes running it externally? I've redone the grounds on the car. Unless I add another wire from.the chassis to the battery?


Generally there is a loop, which forms a coil.
So you want the ground next to the power to minimise the loop area.
And also attach it all in a common place so there is no differential.
They have the characterist that they can be particularly difficult to work out.

It is did not it on a bench because Pops work, because he did not have a ground loop on the bench, so it is good to know that it is not the amp.






Ground loop (electricity) - Wikipedia







en.m.wikipedia.org


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