Hi,
I thought that perhaps it might be of some interest to those who hate finding loosy wires or PCBs on any kind of mod and like to have things a little bit tidier.
My design of this custom Pc Engine Duo RGB mod is based on a THS7374 amplifier and the associated components, but squeezed to fit on a relatively small PCB that can be soldered directly to the HuC6260.
Then, another piece of the kit is a breakout PCB that connects to that PCB using a flex to avoid wiring and changes the pin arrangement to a DIN-8 connector, using the Mega Drive I pinout.
I attach some pictures of it:
Amp PCB soldered to HuC6260 IC:
DIN Breakout PCB:
Amp and breakout PCB installation using the flex cable on a recapped PcEngine Duo:
There is a small caveat on the installation: it's tricky and delicate. Castellated holes of the amp PCB are very tiny and good soldering equipment and experience is required to avoid a mess.
Another consideration is that since the space between the PcEngine Duo PCB and the metallic cover is so minimal, adding the amp PCB with the FFC connector avoids that the main PCB could properly sit on the pegs.
A small opening in the shielding allows to avoid this and makes enough room:
This is how it looks on the case AV connector. No need to make any hole or modification:
I have designed another internal RGB mod for the original PcEngine, which includes audio amp. Let me know if that can be of your interest and I can publish it here too.