Sorry if this is in the wrong place or been answered already, I did a quick search and couldn't find anything.

My problem is this: I've got a GPS, iPod, and phone. I need all of those to output to one set of headphones simultaneously. Is it possible for me to splice together a set of headphones with another headphone cable and have both play at the same time? Is there a device that will do this? The deal is that it needs to be portable (as in doesn't need an outlet) and preferably really small (as in fits in my pocket).
Thanks.

I wouldn't.
In addition to loading the headphones each output will load the other causing a siginificant voulme drop.

Isolate each output with 10k resistors before the common bus.

The total resistance seen by each output is predictable in this config being the sum of the impedance of the headphone load, the resistance of the series resistors and the conductance of the resistors wired in parallel.

and the resistors alone will prevent the interference? am i going to need an amp to be able to hear this after that?

Yes, the resistors will prevent the outputs from loading each other. You may need and amp but not likely if your headphones were already driven hard before the mod.

Awesome. I'll look into the amp, but do you have any suggestions for a portable one (either with it's own power source or powered by a 12V 10mA battery)? I'm going to need all the volume I can get because the headphones are "mounted" in my motorcycle helmet and it can get loud in there.

http://www.headphone.com/products/headphone-amps/the-mobile-line/

Awesome. I'll look into the amp, but do you have any suggestions for a portable one (either with it's own power source or powered by a 12V 10mA battery)? I'm going to need all the volume I can get because the headphones are "mounted" in my motorcycle helmet and it can get loud in there.

Take a look with Google for small, battery powered or maybe even passive mixers. They exist.

I think you should be paying more attention to the motorcycle driving than all that other stuff going on. ;) Wouldn't want you becoming another statistic prematurely.

Take a look with Google for small, battery powered or maybe even passive mixers. They exist.

I think you should be paying more attention to the motorcycle driving than all that other stuff going on. ;) Wouldn't want you becoming another statistic prematurely.


That's why I'm putting old open headphones in. the earbuds were blocking sound (like cars approaching). Hearing the GPS give directions instead of looking down at the mount has got to be better. The phone might be going overboard. Thanks for the concern though. ;)

one more post to get to post urls

I'm building my mixer. Mostly cuz I'm short on cash. Also, because it's a challenge. I'm starting with the schematic from the Rolls MX42 4 channel passive mixer (http://www.rolls.com/data/mx42man.pdf) but swapping the RCA inputs for 3.5mm jacks. I'm adding a DIY 9v amp (see comments for schematic: http://www.creativemods.com/forums/viewtopic.php?p=46831) before the line out actually gets out of the MX42 schematic. Just wanted to say thanks for the help. I'll let you know how it ends up.

You absolutely should use a mixer in my opinion. There are small, compact, and affordable mixers (sub-$100). A 3 stereo pair line level mixer will work. Often those mixers will work as better headphone amps than your iPod, too.