Hi guys,
I've just installed a new head unit in my jeep and am very proud of myself for wiring everything neatly including the audio cord (3.5mm headphone jack) connecting the satellite radio receiver to the unit HOWEVER there is a high pitched whine coming through the speakers when I have AUX selected which coincides with engine rpms. This is likely alternator interference. I would like to install some kind of low pass filter in the audio cord going to the sat receiver, from what I've read, an RC unit with a series resistor and parallel capacitor is a good choice, but I am unsure of what values will filter the whine while still allowing clear sound. Any advice is appreciated!
Joe

 

Here is something cheap tricks to test first. First if not done yet I would have connected the radio directly to the battery. Second try an audio transformer in the audio line between the radio and the amplifier.

 

I think I may be experiencing a ground loop problem. The stereo and the sat receiver are wired to different places that eventually ground to the frame of the car. If I were to wire there grounds together, would that help solve the problem? It would also solve the issue of having to turn off the sat receiver manually, instead it would power on/off with the radio.

Otherwise, what would a good low pass filter solution be? What is an audio transformer?

 

Hello,

Audio transformers can be found in old modems.
They look like the one in the link:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=MT7207-ND

Bertus

 

I think I may be experiencing a ground loop problem. The stereo and the sat receiver are wired to different places that eventually ground to the frame of the car. If I were to wire there grounds together, would that help solve the problem? It would also solve the issue of having to turn off the sat receiver manually, instead it would power on/off with the radio.

Otherwise, what would a good low pass filter solution be? What is an audio transformer?

Google audio transformer and you will find out. Your Google is as good as mine It is also important that all power lines have good connections. And that the power lines are connected properly to the audio equipment. Do you have any documentation in PDF format?