Speaker Noise

[lkv0315]

Hello all! Just got done doing a full audio system overhaul alongside my previously installed Kenwood DNX893S with some Infinity Kappas, Polk Subwoofer, Infinity Reference Series Amp and an MXT sub amp. After driving with it for a few days I noticed the noise that occurs both when music is or isn’t playing, is unacceptable.

Here’s my symptom list so far:
• lots of noise in the system, no matter the volume (static sound)

• an overpowering buzzing sound that occurs under three situations; having the car in reverse, pushing the brake pedal, turning the headlight switch to anything but off.

• very strange (possibly unrelated) short blip of the red battery indicator light (probably like half a second) every time you switch from gear to gear


So far the following things I have tried with little success (just to expedite the process and avoid wasting your time giving me things I’ve already done):
• Ground Loop isolators on all three sets of RCA’s (it helped but not enough for me to consider successful)

•grounding head unit to the same ground as the amps (which is the spot where the ground battery lead is connected to the body)

•turning my speaker amp gain down (noise goes down with gain, but to make it go away you have to have the gain on minimum, which why even have an amp then...)

Yesterday, I ordered an Antenna Ground loop isolator, since my head unit refuses to turn on unless the antenna is plugged in (so I’m assuming it’s trying to ground through it). Also saw something recommending ferrite cores, either with wire wound around it or as I can find on the internet ferrite cores that clip onto the wire. I didn’t order them yet though because I have no idea what they would fix, if they would help and how I would install/use them.

Finally I’m asking here because I think it’s a bit odd it’s behaving based on certain vehicle functions, and I’m thinking it’s something to do with the wiring of the car itself. Thanks in advance for any help!


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[wpoll]

The lighting system in your car uses a ~1khz pulse width modulated signals to power the lights (including the reverse lights, brake lights etc.). These signals will likely be generating noise that is getting into your stereo.

Chances are one of your audio components is on a power supply not intended for audio loads - check your power connections and make sure they are from a similar location (fuse etc.) to the factory stereo.

[andrewwynn]

+1, but also check your ground straps sure no voltage drop on them. Also, check your alternator voltage

[lkv0315]

Originally Posted by wpoll

The lighting system in your car uses a ~1khz pulse width modulated signals to power the lights (including the reverse lights, brake lights etc.). These signals will likely be generating noise that is getting into your stereo.

Chances are one of your audio components is on a power supply not intended for audio loads - check your power connections and make sure they are from a similar location (fuse etc.) to the factory stereo.

My amps are wired to an open bus terminal on the white/blue box mounted towards the front of the trunk. If anything it’s more likely that the head unit is powered by something incorrect. Also, when you said make sure of a similar location, could I tap directly into the fuses that are assigned “radio” or “navigation” in the front and rear without having to worry about the amps burning out the fuses? Like do I need a bigger fuse then because I believe all the radio fuses are 5 amp.

[lkv0315]

Originally Posted by andrewwynn

+1, but also check your ground straps sure no voltage drop on them. Also, check your alternator voltage

By the ground straps you mean where the car connects to the battery? And do you have to check the voltage right on the alternator or is there somewhere else you can get the same reading?

[EODguy]

Use the hidden menu or if you have it a Foxwell using live data.

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[andrewwynn]

Originally Posted by lkv0315

By the ground straps you mean where the car connects to the battery? And do you have to check the voltage right on the alternator or is there somewhere else you can get the same reading?

There are several but the most important is the engine block ground.

If that fails the computer can't get the correct alternator voltage


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[lkv0315]

Originally Posted by andrewwynn

There are several but the most important is the engine block ground.

If that fails the computer can't get the correct alternator voltage


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What would that look like?

[lkv0315]

As of my most recent check, I noticed some weird behavior. My radio refuses to turn on when the antenna is not plugged in, and upon further inspection, there is a slight pulse between 2.65V and 3.25V across the antenna plug. When I installed my antenna ground loop isolator from Scoshe, it still refuses to power on. Any idea why this is?


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[wpoll]

Originally Posted by lkv0315

As of my most recent check, I noticed some weird behavior. My radio refuses to turn on when the antenna is not plugged in, and upon further inspection, there is a slight pulse between 2.65V and 3.25V across the antenna plug. When I installed my antenna ground loop isolator from Scoshe, it still refuses to power on. Any idea why this is?


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There is something fruity going on there - until you can get the head unit to operate with the aerial unplugged, you aren't going to track this down.

The head unit should be able to be powered up with just three wires connected - power, ACC power and a ground. You won't get sound but it should power up.