Originally Posted by
Ace
I had to deal with this issue on my Top-Loader NES trying to adapt the original 1983 Famicom audio amp to the console. If it was just the 2A03's audio going through, the noise was so faint, it was barely audible, but as soon as expansion audio (from pin 51 of the cartridge slot as that's where it passes on my PowerPak and Famicom to NES converter for this console) would be wired in, the audio became really noisy, noisier than a stock Front-Loader NES. Putting a 2.7Kohm resistor to Ground before expansion audio gets mixed in (via 68Kohm resistor in this case instead of a 20Kohm resistor as the audio is too loud like this) fixed the noise.