I've been working on a project for connecting a Yamaha YM2612 to an arduino and triggering sounds to be played from the chip. I'm having trouble on the audio part of the circuit. I've worked out a lot of the noise in my original circuit but I'm having trouble getting the level of amplification I want (not anything huge, just something line level you can use for headphones). A while back, I modded my Sega Genesis with a custom mod called the Mega Amp (I'll link schematic below). That works 100% and has no problems with making the signal clear and loud. I figured I could just rework that circuit for this project, but I'm not getting the volume or clarity I expected. I'm not sure if this is due to there being something else in the actual Sega console but I don't think it is. I've looked into op-amps and think I have an ok enough understanding of how they work, but I might not be seeing something important. Here is the schematic of what I have on my breadboard as well as the mega amp mod that I used. I broke the mod down into just the parts I think I needed. For the time being, I've only been testing this by hooking up one of the audio outputs on the Yamaha chip and running this through my computer's sound card. Any help and insight for this would be immensely appreciated! I'm still learning and would like to know more! :D
Breadboard circuit: https://gyazo.com/b69beac00f659da8f619841d61877566
Mega Amp mod circuit: https://i.imgur.com/DDulM2r.png
TDA1308 datasheet: https://www.nxp.com/docs/en/data-sheet/TDA1308.pdf
YM2612 Pinout: http://partnumber.datasheet.netdna-cdn.com/pdfhtml/0870/865751/page1.png