Does anyone know of a way to take left and right channels from a stereo amplifier and turn them into one mono channel? I had a computer sub amplifier go out and I want to use the driver for a very small subwoofer. This project is not big enough to justify the purchase of a separate amplifier and I know there has to be a way to merge the two channels into one. This is being used with the center part of an old boom box, 15 watts tops, but I don't want to risk destroying it like I did with an old receiver.