How can i make a USB headset from a psp mic?

Well my old usb headset had a small box attached to a usb cable that converted it into four wires: two for the mic and two for the speaker. Now i just want to know how i could make maybe one of those boxes or have a way to convert the usb into those four wires. Then i could just attach a headphone jack to the wires coming out of the converted usb and plug in a psp headset. So what I'm asking is how can i convert that usb to those four wires? Or if its even possible without making a whole circuit board.