So basically this is a normal audio splitter (two female ports and one male port) with a switch in the middle of it.
This is my first instructable so leave comments and let me know how it is :P

Some friends and I have a set up with a TV, a couple game consoles, and a stereo system. Originally there was a normal splitter on the input for the stereo system so we could have an audio out on the TV as well as a computer plugged in at the same time (so we wouldn't have to go to the back of the stereo system to switch the plugs all the time). The problem with this however was that whenever one was turned on or off, the volume would half or double, meaning there would be a sudden deafening blast of sound or everything would get quiet and someone would have to get up and adjust the volume.
To fix this I came up with the idea of making a splitter that had a switch on it that we could put next to the controller for the stereo system. This way whenever someone got up to turn on the stereo system or a console, they could switch the audio input, thus no more annoying volume changes.

What you will need:
-Wire (three colors would help but isn't necessary)
-1x Male audio port
-2x Female audio port
-2x Small switches
-Soldering iron (make sure you solder in a well ventilated area!)
-Solder
-Hot glue gun and sticks (or something else like shrink/crimp tubing or electrical tape to cover exposed wires)
-Some strong glue (ie. super glue, crazy glue)

Step 1: Prepare the Wires and Male Port

Strip both ends of each of the three wires and twist the ends so they are easier to solder.
Repeat this two more times to have three sets of three wires.
As I said before, three different colored wires would be helpful so you can tell which is left, right, or ground. If you want to use only one color, you could color the ends of each piece with a dry erase marker or something to help tell each apart.
The wire was twisted by lining up the ends of three lengths of wire, putting them in drill, and having someone use the drill while you hold the other end of the wires. The knot is just so the wires don't unravel.

The male audio port was salvaged from a broken pair of speakers I found in an electronics dump. In most cases you'll find a white, red, and black wire inside the larger wire casing. Red is usually the right channel, white is usually the left channel, and black is usually the ground. In the port and wire I used, red was right, white was ground, and gray was left.
If these aren't the colors in your wire and you happen to have a voltmeter, don't worry. You can place one lead of the voltmeter on a wire and the other end on part of the port to tell which wire is which. Also, in the case with this type of wire (separated into two lines, each containing two wires) the common color in each is the ground. If you need to use a voltmeter, the tip of of the male port is the left channel, the ring is the right channel, and the sheath is is the ground.

Step 2: Soldering the Male Port

Clamp the wires you twisted and the wire on the male port.
Twist the ends of the wire around each other to make soldering easier.
Solder.
Repeat for the other wires.
If you have two ground wires, just solder them both into the same colored wire you're using as the ground wire.

Step 3: Soldering the Female Ports

Most female ports only have three pins, one for ground, one for left, and one for right (same as a male port).
The part that touches the tip of the male port (the farthest one in) is for left, the one that touches the ring on the male port (the middle one) is for right, and the one that touches the sheath on the male port (the one closest to the opening of the port) is for ground.
If you bend the wire around its pin, it won't move as much making it easier to solder.
For some reason the ports I used (salvaged from broken CD drives) have five pins. After removing the back panel I found that two pairs of the ports (the ones for left and right) were touching, so I bent the pins toward each other to make soldering easier.

Step 4: Soldering the Switches

Glue the top plate of each of the switches together.
Glue each of the nubs (the switchy part) together.
Solder the left and right channel wires attached to the male port onto the middle pin on either switch.
The reason two switches are used is because one switch only has room to change between two pins. Since this is splitting between two audio cables, we need to change between two sets of two pins.
The switches were salvaged from something from an electronics dump. I used them because they were small pretty much exactly the same except one nub was longer than the other.

Step 5: Finish Up Soldering

Finish up the soldering by soldering the left channel of each of the female port wires to the other pins on the left channel switch and soldering the right channel wires to their corresponding pins on the right channel switch.
Solder the ground wires to each other. I tucked them under the switched before soldering so they'd be out of the way.
I cut away parts of the large, grounding, structural pins since they were in the way. If you do this, you may want to keep a little on the switch and bend it over so the switch doesn't fall apart (also make sure they don't touch the pins if you bend them).

Step 6: Covering Up Exposed Wires

Since I don't have any shrink tubing or anything, I use hot glue to cover up exposed wires.
Make sure you get all sides of a wire, hot glue tends to solidify before it gets the chance to wrap all the way around a wire.
Please excuse the amount of hot glue, I tend to use too much.
Also, make sure no wires are touching when you cover them in hot glue.