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Old 04-05-2007, 03:39 PM   #1 (permalink)
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Default car pc speaker hum

in my car i have a mini pc under the seat, this is then linked to the usual car amplifier.

anoyingly the pc sends out a hum, when you turn the volume up it goes up to.

there is no AC voltage in the car what so ever and it is compleatly independent of anythign engien related so im wondering why the pc does it?

any music compleatly drowns it out as its pretty quiet and the music is very loud! but its noticable when no music is playing and hte volume is medium/high.


Ralph
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Old 04-05-2007, 04:05 PM   #2 (permalink)
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Default Re: car pc speaker hum

that is a 60hz AC buzz. If you can start your car, you have power. Your speakers don't run on DC, so you have AC whether you like it or not. If the speakers are powered by your car, then it all connects together. If you plug them into a wall, then its separate. Everything connects to the same battery.

Your audio source and you're speakers are on different grounds, creating the buzz. Either that, or you have a cable connected the opposite way it should be, or it just doesn't have a ground wire in it. You can either try to solve this problem by changing the cable to a shielded cable that will carry a ground, making sure all sources are on the same ground, or you can try a direct box/hum eliminator of some sort to jimmy-rig it together. These will take the audio source and lift the ground out of it, eliminating the buzzing.

Also, check both the signal-to-noise ratio (SNR) of both the soundcard/onboard audio as well as the speakers, the amplifier and the headunit.

EricB may also have some suggestions
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Old 04-07-2007, 04:20 PM   #3 (permalink)
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Default Re: car pc speaker hum

I need to a daigram on how you have the mini pc hooked up. you might need an isolated dc powersupply for it. partsexpress used to sell them, but I don't know about now.
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Old 04-07-2007, 09:31 PM   #4 (permalink)
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Default Re: car pc speaker hum

Hello,

Couldn't he use a ground loop isolator? Would that fix his problem...?

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Old 04-07-2007, 11:32 PM   #5 (permalink)
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Default Re: car pc speaker hum

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Originally Posted by Alvin.C View Post
Hello,

Couldn't he use a ground loop isolator? Would that fix his problem...?

yes. but those things will takes out sound too. if it were just for bass, I"d say go for it, but not for your mid and highs. most people don't noticed the difference, so he can try to see if it works

I like to fix the problem. I use to be the ground loop, engine noise isolator king for people that had this problem. none of my install ever had noise
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