I'm quite happy with the accuracy of my NSF player by now, so I've started looking for ways to (optionally) fudge things to improve sound quality beyond actual hardware. So far I've tried four different hacks, with varying degrees of success:
N163 overclocking
The obvious brute-force solution to the ringing and aliasing this chip produces. Examples: any N163 game. Downsides: none.
Halt APU triangle on periods 0 and 1
Gets rid of the popping sound when the triangle is "muted" by setting it to an ultrasonic frequency. Examples: Mega Man 2. Downsides: none.
APU pulse DC removal
Reduces the crackle that occurs whenever a pulse channel's level changes. Examples: Kid Icarus, The Legend of Zelda, Dr. Mario.
Downsides: causes a low-frequency buzz on some tunes (Mega Man 2 NSF track 13, Dr. Mario NSF track 12). Probably a bug in my implementation, though I can't seem to figure out where.
APU pulse linear mixing
Fixes the crossmodulation artifacts on some games - mostly FDS titles, for some reason. Examples: Kid Icarus, Doki Doki Panic.
Downsides: alters balance slightly, and some games seem to do it on purpose, like the metallic pings in Solstice.
Does anyone have anything else to add to the list?
N163 overclocking
The obvious brute-force solution to the ringing and aliasing this chip produces. Examples: any N163 game. Downsides: none.
Halt APU triangle on periods 0 and 1
Gets rid of the popping sound when the triangle is "muted" by setting it to an ultrasonic frequency. Examples: Mega Man 2. Downsides: none.
APU pulse DC removal
Reduces the crackle that occurs whenever a pulse channel's level changes. Examples: Kid Icarus, The Legend of Zelda, Dr. Mario.
Downsides: causes a low-frequency buzz on some tunes (Mega Man 2 NSF track 13, Dr. Mario NSF track 12). Probably a bug in my implementation, though I can't seem to figure out where.
APU pulse linear mixing
Fixes the crossmodulation artifacts on some games - mostly FDS titles, for some reason. Examples: Kid Icarus, Doki Doki Panic.
Downsides: alters balance slightly, and some games seem to do it on purpose, like the metallic pings in Solstice.
Does anyone have anything else to add to the list?