Multiple AUX inputs, two MP3 players, report
 

I had this on another section of this site, and it was suggested to me that I try it here, so here goes.

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Hi,
First post on this site, so I'll make this brief. I have a 2004 Accord. Bought it a year and a half or so ago.

It came with a radio that has XM in it. It also has what looks to be an aftermarket Honda, MP3player, installed in the dash, as the owner's manual makes no reference.

Now, I want to install another hand held MP3 player and run it into the AUX inout. From what I have seen online, there are splitters that feed both signals into the AUX jack. One is probably in there now for the existing MP3 player.

Now the fun part. Would I be able to introduce another splitter, perhaps at the back of the in-dash MP3 player, so that I can feed the signal from MP3 player #2 into the AUX jack as well.

Will the stereo recognize this third input, as it does the two that are in there now. I would rather keep the in-dash player in, as I do use it.

Does this all make sense?

Thanks in advance.

makes sense. your best bet is to be able to switch between one input at a time. if you try to plug all three in together, each player sees a complex load and you'll introduce noise and possible damage to the players. at a minimum, you'll lose a lot of signal strength as the output device will see two low impedance outputs and one high impedance input. it is important to recognize that for one device to send a signal to another, there is a specific voltage gain relationship. simply put, the sending device needs to have a low output impedance (typically 50 ohms) and the receiving device needs to have a high input impedance (typically 10k ohms). this allows for maximum signal transfer. when you use a Y-adapter to split a signal into two places, you reduce the voltage gain, resulting in less signal and more current from the device.

so what you'll need to do is wire up a switching system that lets you choose between inputs. this is fairly easy as there are only three wires per source. you could use multi-pole switches or relays to achieve your goal. the end result should be a switch or two that let you decide which mp3 player the head unit will see.

note that most people just unplug and plug in other devices. wanting to do something different is fun and something i get into quite often. let me know if you need additional help with circuit designs.