this is my nuby reverb box, it plugs into the bottom of the gameboy and adds a reverb to the pro sound. there is still a couple of things i would like to add to this like an on off button, but i am pleased with how it works
http://www.youtube.com/watch?v=7_MotfEdw-8
i had to make a change to face plate so i made a new one.
i needed to step down the 9v to a steady 5, so i used a gameboy regulator board, they are awesome!
i have a second input just as a through for the original audio jack, but this is not wired up yet as i don't have a 3.5mm jack socket
the two pots and the 1/4 inch jack, i used stereo pots because they are actually cheaper