Lately it seems I've been asked about this several times, so I thought it was time to share this information. And just so I'm not getting too much credit here, this ain't nothing that I thought up. This is pretty Old Skool stuff.
my IntaRide RP-1 intercom. But I ran out of inputs on it when I decided that I wanted to pipe the Valentine One's *beep beep* into my ears. You can't just simply buy a 'Y' cable and share an input with another device. That's a really good way to burn something up. So what I did was build a simple "Passive Mixer". It's VERY inexpensive, a fun little do-it-yourself project, and best of all - IT WORKS!
Here's what you do...
Go to RadioShack and buy:
- A little project box (p/n 270-1801)
- A couple of packs of resistors (p/n 271-1124 if you want 4.7k-Ohm Inputs) & (p/n 271-1126 if you want 10k-Ohm Inputs) I decided on both.
- 2 packs of 3.5mm mini jacks (p/n 274-249)
That totals to about $11.
Not too shabby, eh? Don't forget to buy solder if you're out...or you can't find yours.
Basically, all you do is use the resistors as jumpers and tie all the contacts together. (See the back of the package for the pinout numbers on the jacks.) Connect all of the 'Pin 2' contacts together (aka the 'Tip', or left channel contact). Then connect all of the 'Pin 3' contacts together (aka the 'Ring', or right channel contact). Lastly, tie all of the ground pins together (without resistors) using a small piece of wire (that's the blue & white wire in my pic).
Make sense? Hopefully my pics will clarify things.
As for why I used 10k-Ohm resistors AND
4.7k-Ohm resistors. My GPS and Valentine One have VERY HOT
output levels. The 10k-Ohm resistors do a better job at trimming these levels down a bit. For a music input, I would definitely use 4.7k-Ohm resistors.
So get those soldering guns out, and go nuts! Just don't burn yourself...like you did the last time.