Not all games will oscillate when selecting SBPro, but only those who enable the high-speed stereo mode, and when there are actually stereo sounds playing the oscillation is extremely severe.
Yes, games that put the card in SBPro high-speed mode without having the option to choose SB16 is practically non existent, but apparently Tyrian is one of them.
The distortion problem is much more problematic since most older games like Jill, Supaplex, Skyroads etc.. are very loud and distorting the Vibra16(S) constantly.

Combine the two problems and you get a bad apple, not recommended.
Unless of course it is only my Vibra16S model, we still have to confirm these problems with other vibra16s cards.

The squeal in System Shock is part of the music, unrelated to the oscillation bug,

Interesting stuff thanks James-F. Out of interest, have you ever turned your analytical eye to the PAS16? Like the SB16 its MPU-401 implementation is flawed and should be avoided, but otherwise I think it's a gorgeous sounding card and is often natively supported in games where stereo matters. You do miss out on stereo in Wolf3D unfortunately and there's a pretty outrageous amount of hiss to contend with, but the latter can be handled via the mixer. The (real) OPL3 sounds great on the PAS16 too, as does the SB emulation.

No, I haven't had a chance to test a PAS16, sorry.
I created a small list of test points that are part of my procedure of testing sound cards.

* No Distortion in high volume games.
* No Oscillation in SBPro high-speed Stereo mode.
* No Clicking after sample playback.
* No noise from Wavetable header amplifier.
* Low Harmonic Distortion playing -0.1dbFS 440Hz sinewave in 8bit and 16bit.
* Capable 8-bit to 2/3/4-bit ADPC.
* Present Dynamic Lowpass filtering.
* Working Mixer.
* Authentic OPL3.
* Bug-free MPU-401.
* Low noise, above 70 SNR.

I should mention that Line-Out is not designed to be used with Headphones, it should see a proper 10k ohm load, not mere 16-32 ohms of headphones.
The sound in the headphones will completely lack bass and will be distorted because the chip cannot provide enough current to drive the cones/diaphragms/drivers/transducers.

Currently not a single card completely passes all the tests, and there probably isn't one.
DOSBox comes close with Nuked-OPL patch but lacks a proper Lowpass Filtering.

Once the CT2230 is here I'll review it comprehensively.

So I bought a CT2940 w/ real OPL3 on eBay, and before it gets shipped to me (which will take a while) I have to ask:
Does this card have the DMA "click/pop" bug like the old SB16 cards? And does it have the Vibra "ringing" problem? It's a Vibra CT2502 chip after all...
Also are there any downsides with this card except for being PnP?