Need help getting rid of alternator whine

[Bigpav7]

Got a situation here I cant figure out. I bought a dvd player and 2 headrest monitors for my car. I didnt want to hardwire the dvd player to the car so I wired it to a power adapter (well, 2 of them to make the cord longer) and plugged it into a power outlet. The dvd player is connected to one of the monitors using RCA wires. Another set of RCAs connects this monitor to the second. THe constant power for the monitors comes from a wire hooked up to the battery. THe switched power comes from yet another power outlet (spliced). Both monitors are grounded to the same bolt (is this a ground loop?). That's about it. I get extremely annoying alternator whine in both monitors (built in speakers). Please help figure this out. Should I go with more expensive wiring for video/sound from the dvd player to the first monitor? what else can it be? none of the wires really run alongside each other.

Thanks in advance.

 

[DSM1G90]

Yep, you got "ground looping" - don't tie your grounds - isolate them. For you got battery ground and chassis ground in all cars.

Sounds like quite the electrical/blacktape configuration there. Make sure it's not taxing out the alternator or it will die on you as well.

 

[Bigpav7]

thanks DSM. I'll separate the ground and see if that helps. Does the quality of RCA wires matter at all when it comes to interference?

 

[Kastigir]

thanks DSM. I'll separate the ground and see if that helps. Does the quality of RCA wires matter at all when it comes to interference?

Absolutely, some are shielded better than others.

 

[Bigpav7]

i tried a noise filter (ground loop). did not help. swithced to better rca's and separated the grounds. Still nothing. I am officially out of ideas..

 

[DSM1G90]

Okey, I can see it now (Review and correct me )- do you have a "Y" splitter feeding the other monitor from the first monitor?

You got one of those 12v to 120VAC inverters to feed a regular DVD player, or is one of those in-dash DVD player units that you have in your car?

What about just one monitor and leave the other one disconnected - is there ALT whine in that one monitor? And, when you connect the other one, then does the whine come back?

Even with shielding, we still need to ground the shield to send that noise to ground and get rid of it.

Just some ideas... good luck - DSM

 

[rush2252]

run the RCA cables as far from the power supply or power wires as possible. If you have the RCA wires anywhere near the power supplies or cords you will see alternator whine as well. And yes the quality matters as mentioned already

 

[Bigpav7]

thanks for the advice guys. I am going to try to hardwire the dvd player to the car (it's an in-dash currently wired to a power adapter plugged into the cigarette lighter). May be this way the ground would be better. I'll just stick it into the glove box. One of my power wires is hooked up directly to the battery. Is there a good or a bad way of doing that? I just wrapped it around the positive terminal bolt and tightened the nut up. I started thinkin that may be this has someting to do with the whine.