Step 1: Tools and Supplies:
-Drill w/ bits
1x Project Box
1x DPDT switch
3x 1/4 Mono jacks
Step 2: Preparing the box
Take you project box (i used a plastic one from radio shack, if you use a metal one you'll need to insulate the inside of the box with electrical tape) and drill a hole on the lid of it.
Then, turn the box on its side and drill another hole for the 1/4 jack.
do the same to the other side.
then, drill a hole on the top of the box for the 3rd 1/4 jack.
Now your box is all ready.
Step 3: Wiring Time!
Follow this diagram.
*All you have to do is connect the Tip on output A jack to the 1st and 6th prong on the DPDT switch.
*Next, connect the tip of the Input jack to the 3rd prong on the DPDT switch.
*Then, connect the tip on the Output B jack to the 5th and 2nd prongs on the DPDT switch.
*Finally, connect the sleeve of Output A to the sleeve of the Input Jack, And then connect the input sleeve to the sleeve of the Output B jack and finally connect that to the 4th prong on the DPDT switch.
Now, the wirings done :)