i mod all my gameboys this way to keep the headphone amp intact, and then just drill a hole in the case and use a separate 1/8" stereo jack for pre-pot line-out. i don't want the (usually dirty) volume pot in my line-out signal, and i like using the headphone output while i'm writing on headphones. but if i plug the gameboy into a mixer or something other than headphones, i use the line-out jack.

This is typically how the pro sound mod is done. You can alternatively add a DPDT switch to make the headphone jack toggle between prosound and the amplified output.

For how simple and effective the prosound mod is, it becomes impractical and unnecessary to recreate the amp circuit. It's been done, but I don't think the primary intention was to remove noise.

Yeah you can totally do that! I wouldn't recommend using both of them at the same time though. Just use one or the other!

I'm not sure how noisey the headphone amp itself is... Even in my dev board where the CPU is the only original part the output is still kinda noisey.

hi, this is a quick question i had, would it be possible to do the prosound mod (pre-pot) and keep the headphone amp signal functional so when i wanna just use my headphones for composing?

I was wondering if the headphone amp circuitry being still intact would affect the output of the line level or as long as i dont have a headphone plugged in i can run a line out?

normally it would be line out for shows/live PA, headphones for composition.

also since the headphone amp circuit is noisy and not that great... would it be better to make anther DIY headphone amp circuit instead? has anyone done this before?

thanks