How to use 2nd amplifier in a Sega New Astro City

[Pinball]

The PSU provides a weedy 8W to the small speakers. Very quiet, and particularly with a RaspberryJAMMA as the Pi has no built-in audio (or video) amp. I recently upgraded the speakers and it's got even quieter :-(

However, there is a large amp beneath the PSU which is unused (see photo). The 'sound out' will connect to the speakers via the nearby male-female connector (same yellow colour), but there is no connector for the 'sound in'.

My question is- how can I use this amp? For example, could I get an adaptor (where from??) for the yellow female plug (connected to speakers) and route it via the amp to the speaker plug? Does using 2 amplifiers in series like this cause an issue?

How is the amp normally used? I'm guessing with stereo PCBs, but I'd like to give the mono audio a bit of extra power...

 

[Westcb]

Sound from Jamma line goes into sound in, then back out to sound out. Your speakers have a clip like that in the cab. You may need to throw together some cabling but yes you can get the connectors you need to do so, arcade otaku lists the model numbers you are looking for. I think I got mine from mouser or digikey last time including the pins. Step one is just follow the sound lines from the 56pin connector to the speakers and see what you are working with.