[colliek]

Dearest Audiophiles, I need your expert advice on some Clarion WH100 wireless headphones I recently purchased for use with a portable dvd player for my backseat-dwellling-kids.

Please keep in mind I have no idea what I'm doing.

The earphone set I purchased has an IR transmitter that's designed to be hardwired into the car. Since I didn't want to to that, I wired it to a 12v cigarette lighter adapter from Radio Shack. That part of this adventure seems to be OK.

Then, I realized the IR transmitter had two female audio plugs, and so does my DVD player. So, I found a cord that has two male plugs on one end, coupled it with IR transmitter, then plugged the single male end of that same cord into the headphone jack on the side of the DVD player.

Believe it or not, it works and I can hear the audio from the DVD on both sets of headphones.

However, my problem is this: I'm getting what seems to be engine noise interferenece in the headphones. It's the same pitch as the engine, and I think (but haven't had the time to confirm) that the noise shifts in pitch when the engine shifts/revs.

Any ideas on how to get rid of the static?

I'm totally out of my league, but know youse guys know what you're talking about. I'm just a Mom trying to keep her kids happy on that long trek to Nana's house.

Thanks in advance for your help and good humor!

 

[renov8r]

two ways to address such noise...

...shielding/isolation and filtering.

First I would do a little investigation to help narrow down the cause of the interferance. The simplest thing to do would be to determine if the noise is present when the engine is not running. If it is, you are on the WRONG track. The noise is inherent to the set-up . If you ONLY hear the noise then you can attempt to minimize it.

I would first attempt shielding/isolation, as it is may be easier. If you have found that the noise is present when the engine is running it is probably from interferance in the DC power feed. Attempt to run the headphone unit from an alternate source of DC while the engine is running to verify. THis could be as simple as using enough batteries to give 12 volts (two big 6 volt latern cells would cost around $10 at WalMart). If you have determined that the DC outlet is the culprit, you can most easily shield the leads from the lighter adapter. Just use shielded wire, it has an inner conductor & outer braid-- like coax. Stereo installers will have it and so do most electronics techn stores, like Active Electronics.

Moving deeper in you could attempt to isolate the feeds to the lighter ciruit by putting this on a seperate terminal block. Not as hard as it sounds, something that stero installers do often,

Finally, you could try filtering. In the OLD days you could count on the ignition making RF noise, with its point, condesor & coil, but modern ignitions have all those goodies shielded from the get go, so as to not interfere with the on board electronics. BUT there are lots of other potential RF sources. The circuits that drive the injectors can produce RF. THe displays that provide A/C and Nav info can leak RF. THe speed sensors can generate local RF fields. Very hard to determine if any are causing the noise your headphones pick-up.

And NO, the likelihood of it being was one of those may not be small. Even though all the OEM radio stuff must have been tested/set-up to reject such signals, the adapter/transmitter you got WAS NOT. It may be possible to simply wrapp that box in lost of Al foil, and create a "Faraday Cage" to keep out ALL unwanted RF-- ugly but it woulf work.

 

[colliek]

I love a good mystery!

Renov8r - Thanks for your thoughtful reply, will check it out as you suggested and post the results. Geez, I love this site!