Quote Originally Posted by ooXxXoo View Post
For those that are having sound issues with the NES portion of of the Retro Duo(scratchy sound+missing a few effects), here's a quick easy fix:

Good games to test this mod are Super Mario Bros.3 and Ninja Gaiden(play these for a few minutes so you'll notice the difference)...
Unplug from the Power outlet and Turn on and off the Retro Duo for a few seconds before doing anything else, so you'll get rid off any remaining current left....After completely carefully taking apart the RD motherboard from the shell, look at the back side of the NES portion(near the AV Jacks and closest to the NOAC)..Please ignore the gray ribbon wires, they belong to another mod...



Look directly at the NOAC and right above it between the NOAC traces,you'll see the words "rest" and "sound" written near the actual NOAC..There is a solder spot right under the word sound(This word is going to be found nearest to the Red RCA jack)



Get yourself a 0.1uf ceramic capacitor (104)...Add a bit of solder to this point under the word "sound" and attach a leg of the ceramic cap there....The other leg should be connected to the ground side of the White Rca Jack connector...(as show in these pics)..





Make sure to shield this new cap legs connections or you may experience a bit of ghosty lines on the video, not a huge problem though.....

After this, your NES games will sound just fine.....This worked great for me...And if anyone tries this, let me know if it worked for you..
i just got a retro duo and the sound was kind of off with a few games... i did this mod and it works much better now. just wanted to say thanks, because i haven't seen this anywhere else and it's such an easy fix.

i also soldered the wire from a broken snes controller to a nes controller. if anyone doesn't know, the wires match almost perfectly, just swap the red and yellow ones.