What You Need:
-a Rock Band mic
-a 1/4" mono jack ($4 for a pack of 2 a radio shack)
-a blank or unimportant CD or DVD or a washer with a 3/8" hole and a total diameter of about 1"
-a soldering iron
Step 1: Opening the Mic
Opening the microphone is the most difficult step of the entire process. You should start by cutting the cord about 1-2 inches from the base of the microphone. Then comes the hard part: Twist the top "cap" part of the microphone until the screws on the inside break and it comes free. After you do this, remove all of the internal components and discard the weight in the center of the microphone. Remove the rubber plug thingy from the bottom of the mic body.
Step 2: Soldering the Jack
Splice the black wire coming from the microphone part about 1 inch from the end. Inside there is a white wire (the lead) wrapped with bare copper wire (the ground). Twist together all of the ground wires. Splice the lead about 1/4" to 1/2" from the end and twist together all of the lead the wires. Solder the lead wire to the tip part of the jack. Solder the ground to the ring part of the jack. After you've finished soldering, plug it into a guitar amp or pa and make sure it works.
Step 3: Making a Plastic Washer
Cut a short strip from the edge of the CD and pull apart the 2 layers. Throw away the top label layer and keep the clear plastic layer. Cut a square in the clear plastic about 1" x 1" and keep cutting the corners off until you have a circle with a diameter of 1". Use a knife and place the tip on the center of the small plastic disc you just created and keep turning while applying pressure until you get a hole with about a 3/8" diameter. I used a 3/8" drill bit to check the size of the hole. This might take a while.