I hooked up my Sega Genesis Model 2 and rgb modded N64 to the OSSC via scart today for the first time and encountered the same noise.
Any other troubleshooting ideas? Downgrading the firmware made no difference. I am starting to second guess myself; would it be worthwhile to uninstall the HDMI Audio Upgrade? I want to reconfirm that I was not overzealous with the knife when cutting the traces between the I2S, WS and SCK solder joints.