Sunsoft 5B/YM2149F highest frequency missing plus slite volume cerve error?

[djmaximum17]

I've tested this with various NSF players, NEZplug++ seems to be the only player that emulates this NSFplay just ignores it, also I think the volume curve is a bit off?
5B_ultrasound_half_volume_test.zip

[bbbradsmith]

If NEZPlug does something differently than NSFPlay this is not something I consider an error. I have no reason to assume NEZplug is correct.

What does it do on 5B hardware, and does that differ from NSFPlay?

The idea that a tone with period 1 could reduce the volume of the envelope is plausible, but I can't make that assumption without seeing the hardware do it. (Does seem to be something that's on my list to investigate though. #7 & #43 )

Similarly, I would not alter the volume curve without a hardware demonstration that contradicts it. The current shape was set to match hardware as closely as I could, for a single channel.

In the long term I'd want have an option to simulate the 5B amplifier circuit in NSFPlay 3.0: https://forums.nesdev.org/viewtopic.php?f=2&t=17745