You are supposed to leave solder on your tips.  After cleaning them well with a wet sponge or the metal ball(my preferred method as it doesn't affect the temp of the iron) you are supposed to apply fresh solder to your tips before turning off the iron.  It helps keep them fresh and capable of distributing heat.

If you have good phones it still outputs at a decent volume but it's clean as stated.  You only hear the sounds made with LSDJ without the background hiss and amp noise.

You're right, I'll try that out. Agreed, I'm very happy with it. Thanks for the help!

how about comparing the sound outputs with an amp. The headphone jack should be quieter than the "pro-sound" coming from an audio amplifier. In any case, the quality is what you were aiming for, so in all honesty it was a success.

Didn't think it was much more quiet? Maybe I subconciously turned a volume up somewhere. The quality was definitely better, so I'm pretty sure I didn't do it wrong

Quieter unless you did it wrong.

Just adding I ended up completing the mod today. Drilled a hole and did it the common way, so I can still use headphones through the old port. But I plugged in headphones to the new port and they worked perfectly fine? You said this shouldn't be normal

Yeah I'll keep that in mind. I've only used this iron for this gameboy. I've got a pretty poor quality case (took the circuit out at some point.. not sure why) which I might experiment with

The first one I ever did was by melting a hole through with my iron's tip. It was a sketchy hole, but with the jack installed, you couldn't tell.

Just take your time and make sure to clean your equipment afterward. You have no idea how many tips I went trough over the years becuase I didn't clean off the extra solder.

Effort, plus ability. Not sure I have the drill bits. I'll consider it.

You may use phones, but it will be very very quite. Clean but quite.
The "effort" As you call it is well worth it to retain the amplified headphone connection.

Wait I just watched a bit of this... (just a note I'm not really looking to drill a hole in my case, will take a bit too much effort).

If I replace the inbuilt jack, will I not be able to use headphones? (This is fine as I can just use a different gameboy if I want to write on the go, and then use the modded one when I want to record).

Awesome - I'll probably find some padding in some way. So should I be desoldering at the connections? Or can I just cut and insulate?

Or you could just use the old jack that's in the gameboy and still bypass the amp. This tut goes into more detail: http://lowgain-audio.com/GBclassicmod.htm

Removing that board will cause no issues, but the trouble will be in finding a jack to fit snugly.