newbie question about car audio

[drumlicks]

Hi guys, I'm wondering if anyone can help with this problem: I have a Garmin GPS unit which has a stereo mini-plug out, an XM Satellite Radio with the same stereo out, and I've used a stereo mini-plug splitter to hook them both into the one auxiliary channel I have on my truck stereo...the problem is, when I plug the GPS and the sat radio in simultaneously, the signal from the XM cuts about 60% and loses the stereo sound...as soon as I unplug the GPS, it returns to normal...am I supposed to have the same ohms running from both devices to make them both work on the same channel? I really appreciate your help, if someone could help...I'm not electronically knowledged enough like you folks...thanks much, Aaron Worley

 

[Diver300]

Hello and welcome to the forum.

I assume that you want the GPS connected to give you occasional directions while you listen to the radio most of the time.

The problem you have is that two audio outputs are not designed to be connected together. It sounds like the GPS is mono so it only has one output, and that one output is connected to both the left and right channels. That connects the channels together and so you loose the channel separation.

You should fit resistors between the GPS and radio ouputs and the stereo input. You will loose some volume. I suggest starting with 1 kΩ for each resistor.

The ground connection will be the outer connections of the jack plugs. It doesn't matter which is the left and the right as you treat them the same.

You can adjust the resistor values to get the GPS volume the same as the radio volume. You should keep R1 and R2 the same value, and R3 and R3 the same value. If you increase R1 and R2, it will make the GPS quieter.

The good news is that you can fit the resistors to the stereo mini-plug splitter so if you mess it up you just buy another of those. It is also almost impossible to damage the GPS, radio or stereo whatever value resistors you use.