Hello!
I have a question for you guys: I'd like to make a prosound mod on my GBA SP but i can't find any schematics, so, could someone help me with a schematic or a how-to?
I see there's a way to make it but I didn't find any image >////<
Get a gba sp headphone adapter for like $5 on ebay.
http://forums.modretro.com/viewtopic.ph mp;t=11746
This is a project log of GBA SP inside the DMG shell. At some point it explains how to wire closed circuit headphone jack. You could use that. But headphone adapter is the easiest and most straightforward way also does not require shell modification (and SP is a bitch in terms of free space).
My friends that use gba sps for chiptune all use one form or another of headphone adapter.