Question about APU1 mixer

Discuss NSF files, FamiTracker, MML tools, or anything else related to NES music.

Moderator: Moderators

Post Reply
User avatar
Yave Yu
Posts: 39
Joined: Sun Jan 19, 2014 6:15 pm

Question about APU1 mixer

Post by Yave Yu » Tue Jan 19, 2021 5:29 pm

APU1: Square 1, Square 2
Most people said "non-linear" is more accurate to NES, however I heard some audio from some real machine video such as SDA, like Mega Man 2's staff (loud square wave, a clip with two 75% square waves plays), it's not very "dirty" than any exist "non-linear" mixer.
So please tell me, which mixer is actual "accuratest" to real machine?

lidnariq
Posts: 10241
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: Question about APU1 mixer

Post by lidnariq » Tue Jan 19, 2021 5:45 pm

The square wave channels are pedantically non-linear, in that the volume of two square waves at maximum volume is slightly quieter than twice the volume of one.

The DAC has perfectly fine "differential nonlinearity" but rather lousy "integral nonlinearity", but because the DAC is only being used as a volume control instead of prerecorded sample playback, the effects are pretty subtle, and may not be audible.

None-the-less, two pulse waves of equal volume playing 75% duty should be ever-so-slightly quieter than two playing 25% duty.

Post Reply