[YM2612] Low-pass filter options, chip type options

[freq-mod]

Sega mega Drive used different audio chips, op-amp, mixers throughout its lifespan. Original Model 1 consoles used discrete YM2612 sound chip with rather prominent ladder effect, clear audio quality, but op-amp differences between revisions meant it would sometimes sound more brighter or more muffled. Because of that, most Mega Drive emulators have an option to enable low-pass filter with user-definable cutoff to emulate this peculiarity. Would it be possible to add this functionality?

Model 2 featured an YM3438 core integrated into VDP ASIC that didn't have ladder effect (however, some revisions of model 2 had a bad op-amp that damaged sound quality, It's hard to emulate these distortions, though).

I don't know if ares's YM2612 emulator supports that, but it would be great to have selection between two types of FM synth.