New enhanced version of Gameboy Color quality loud sound mod is ready. It's called GBAmp2s. It's ready to order at tindie.com
Difference with the previous version is that it is using different amplifier ic with more gain. Also it uses stereo audio signal from Gameboy. And you do not need to install additional capacitor to remove loud hiss/hum from the speaker. A bunch of quality capacitors already installed on the GBAmp2s mod pcb.
Bare and assempled pcbs:
Yes there are couple more wires to get stereo audio to pcb. This new pcb design has all connections marked on silkscreen, so it's easier to install.
New pcbs are made by hqew.net which service I will review later.