GGFM - Yamaha YM2413 Sound module

FM sound is an add-on sound module for the Sega MasterSystem. The FM sound on the Sega Master System allowed for more complex and richer audio compared to the console's standard PSG sound. It offered a wider range of tones, including various instruments and musical effects, which enhanced the overall audio experience of games that utilized FM sound.

Since the Sega GameGear is also capable of running in Mastersystem games, it is also possible to retrofit the add-ons from the Mastersystem to the GameGear. This board is a FM sound add-on module that fits on top of the GameGear mainboard.
There are about 60 Mastersystem games that support this module, if you enjoy playing them on your GameGear - this module is a must!

The Yamaha YM2413 chips are very hard to get, therefor a limited stock is available.

A single premium speaker will fit and is also highly recommended to enjoy this module the most. Due to the size of the module, it does not fit in a dual-speaker shell with 2 premium speakers.

The board comes as a flex PCB, which makes the installation very easy. Just align it on top of the cartridge pins and reflow the necessary pads. Optionally in case you want to play Outrun - you have to run 3 wires to re-route the PSG sound towards the FM sound board.

For the PSG mixing you need to remove R20 and R23 (VA0) or R52 and R54 (VA1) and solder the included wire to the L and R channels. The shield should be connected to ground on both sides.

If you don't want to use the PSG mixing feature - bridge the 2 pads on on the left side of the GGFM board and switch off DIP switch 3.

DIP switch explanation:

1. Enable / disable FM sound module
2. Enable / disable FM sound module muting when not used
3. Enable / disable PSG module muting when not used (enable for Outrun)

I recommend to leave them all to ON position.

There are 2 different type of Yamaha YM2413 chips, the YM2413B variant is a low current variant.

The add-on board has been made based on the SMSFM module from Tim Worthington, a big thanks to him! Without his support this module wouldn't available.