Audio & Power in car: Electrical Noise

[kd5ftn]

I've got a problem when I plug my HTC Titan into my car stereo as well as cigarette adapter.

I'm also got a kind of custom setup using the HTC Y Adapter with a 2.5mm jack and MiniUSB jack

Audio
Honda Civic Stock Stereo -> CD Changer to Aux Input Adapter -> 3.5mm to 2.5mm adapter -> 2.5mm input on HTC Y adapter.

Power
Belkin Cig. Lighter to USB Female Port (From old iPaq) -> HTC Stock Sync/Charge USB cable -> MiniUSB input on HTC Y adapter.


So, when both the power and audio are plugged in, I hear a horrible hiss on my car stereo, not to mention a sound that varies in pitch to my throttle. When I unplug the power, the audio is completely clean. To me this seems like some kind of a grounding issue - to say that the Audio and Power both have seperate grounds, and bridging the two creates a potential difference in the form of noise on my Sound. Also to note: I only hear the noise when the Y adapter is plugged into the phone. With the audio and power plugged into the Y adapter, but the Y adapter not plugged into the phone, It's perfectly clean. I'm kind of baffeled.

The only solution I can think of is to gut the Belkin Power->USB adapter, and providing it from 12VDC elsewhere. I've got a tap directly below my passenger seat where I have a big power inverter tied to my battery. I don't know if I'd hear the same sound by grabbing my power from there.

Anyone with an engineering mindset have an idea? I'm open to suggestions.

[LGSilva]

You are right, you have a problem with ground.
I have the same problem with a mp3 player. When I plug the audio + power I have noise, just audio is fine.
You may try the inverter as it would probably filter the noise you're getting from the DC power in your car.

[delboydell]

you just nead an in car ground loop isolator used for getting rid of noise on the low level signal to amplifiers.They are just a 1:1 audio transformer
Any incar hifi shop or ebay will have plenty.

[speakerphone]

I have the same problem, with a polaris using standard headphones. I'm thinking the polaris itself has issues dealing with audio+charging

[cones]

i had the same problem with an ipod charger, sent the car to the wreckers, and woot, problem solved :P sorry that was no help :P

[CoMoCHenGA]

Usually happens when the signal wires (mm adapters + input cord) aren't shielded and pick up the magnetic field from the ground resulting in the engine noise. Sometimes, making sure the signal wires are not touching the power cord and keeping them separated might help. I'm not really sure, since I'm a 100% noob too all this. Let me know what your fix is. I'm not too hip on all the car audio stuff anymore, but if you wanna put some hydraulics in your ride, then I can definitely help you out.

[speakerphone]

more likely the problem is in the phone, so ...