The CT2890 is here.
No clicking noises in Prince of Persia.
Ringing in Tyrian, Descent, MPXPlay, all in SBPro Stereo (high-speed) mode.
Distortion in high volumes which can NOT be fixed with the mixer.
OPL3 sounds good.
Good balance between FM and PCM.
75 SNR (great).
Buggy MPU-401, hanging notes and stuttering Duke3D.
The ringing happens when the card is put in SBPRO Stereo (high-speed) mode, which we know SB16 don't do at all.
This can be also recreated in Descent setup choosing a SBPro and playing Test Digital Sound Card.
Tyrian apparently forces the card to SBPro high-speed mode.
Furthermore, when only the left or right channels play the oscillation is extremely severe.
This side effect resembles parasitic oscillation as it is called in electronics caused by incorrect feedback.
Distortion can be heard with especially loud games that cannot be lowered in the mixer, it was not so with the CT2950.
To test this: Doom, Sound max volume, idkfa, weapon 6, shoot straight ahead, you'll hear a crackling sound which can be fixed by lowering the VOICE mixer of the SB16 but not with this card.
Another quick test in Skyroads when the ship explodes.
Lowering the volumes in the mixer lowers the distortion along with the sound, whether on the CT2950 it eliminated the distortion completely.
So the distortion is generated before the mixer and cannot be removed.
After some further testing it appears that the CT2230 and CT2950 also oscillate in SBPro Stereo speed-mode not only the Vibra, so this problem is common to all the SB16 family.
The distortion occurs at the utter most loud games, not something that is noticeable with other more normal sound level games.