There seems to be an audio bug or performance issue that results in audio clipping in all of the cores I’ve tested. I’ve tested this in all stable releases from 1.9.0 to 1.9.5. The last version to not have this issue was 1.9.0.
It’s not obvious unless you really listen for it, but I’ve uploaded an audio clip comparing the before and after. The games in the clip are 10 Yard Fight (FCEUmm), the Sega CD BIOS (Genesis Plus GX) and Super Metroid (Snes9x 2010). The 1.9.0 audio plays first, followed by 1.9.5.
Default settings were used in both releases and the recordings are from line-in.