Tried pure DOS and no difference... Pretty sure it's just the card?

Most SB16s suffer from clicks and pops when they try to play back audio written for the Sound Blaster Pro 1/2 and prior cards.
The issue is caused by the way single-cycle DMA transfers are handled by the sound card's chipset. Sometimes it's more obvious on some systems/software setups, but one thing is guaranteed, you're going to get clicking and popping at some point (unless it's a ViBRA16 - more on this later).
Unfortunately there is no fix for this issue, short of either using a SoundBlaster 16-specific setting in a game (which bypasses the single-cycle DMA issue entirely), or using a non-SB16 card. Some cards (ViBRA16) have different glitchy behavior when handling single-cycle DMA transfers: instead of clicks and pops, you get faint high-pitched ringing or hissing sounds after a sound is finished playing. Depending on your tolerance this may actually be less annoying than the pops/clicks.

Doom should have its own SoundBlaster 16 setting, so it won't give clicking or popping audio. Day of the Tentacle IIRC is one of those single-cycle DMA games. Another single-cycle DMA game is the CD talkie version of Star Trek: Judgment Rites, that game will click and pop pretty badly on a non-ViBRA SB16.

Yeah, sounds like the single-cycle DMA bug.

Note that SB16 cards suffer from several issues as described here:
Sound Blaster 16 Bugs and Deficiencies Summary

Some models suffer from more issues than just those, too: at least two models have unprofessional design mistakes like floating op-amps, which make the cards noisier than they ought to be.
I'll put my notes in that Bugs and Deficiencies summary post shortly.

Thanks for the info guys! That is a real shame I grew up on the SB16 sound and had thought this card was free of issues - turns out none of them are... UFO is one of my favourite games ever so I may consider replacing my card just for that

telecommand wrote on 2021-01-04, 02:25:

Thanks for the info guys! That is a real shame I grew up on the SB16 sound and had thought this card was free of issues - turns out none of them are... UFO is one of my favourite games ever so I may consider replacing my card just for that

There is no sound card that does everything perfectly in every piece of software. However, if you combine a few sound cards, you can come pretty close to perfection, IMHO .

Combining an SB16,SB32, AWE32 or AWE64 with a good quality SB Pro and WSS compatible third party card (Crystal, YMF, Opti or Aztech based) will get you great compatibility with practically every DOS game under the Sun .

Don't forget the Media Vision Jazz16. That has been offering pretty darn good SB Pro support for me, it's worth pairing with an SB16 for the stuff that doesn't need an SB16. Just bear in mind that its MIDI output (not related to the FM) is even more useless than the SB16's.

Having tested the CT2290 with UFO enemy unknown, there are graphical glitches and the pops are loud and clear at the CPUs original speed (here an Athlon XP @ 1666 MHz) when a mission starts. However after L1 is disabled the graphical glitches and pops disappear completely. Please keep in mind I'm running the game from DOS 6.22 directly.

Here is a good discussion of the topic: Sound Blaster 16 Bugs and Deficiencies Summary

Essentially, in the CT2230 you do have one of the best SB16 models which does have the least number of problems, but these sorts of single cycle DMA clicks do occur nevertheless. I have set my system up with two sound cards, using the SB16 as the main soundcard for Windows and newer DOS games and a different card for older DOS games which have this problem.

Thanks for the info Lazer42. Are there particular old DOS games you could recommend to test this specific issue?

cde wrote on 2021-05-31, 07:36:

Thanks for the info Lazer42. Are there particular old DOS games you could recommend to test this specific issue?

The game I've found where it was most noticeable to me by far is Mickey's 123. See the video here to hear an example: https://youtu.be/gYHvWLrsF-4

I have also found Wolfenstein 3D exhibits it, though not nearly as badly as that.

Thanks a lot. I tried Mickey's 123 (enhanced) with L1 disabled but did not hear any clicks/pops. The sound effects were fine although of a low quality. Maybe using the CT2290 in a relatively modern system (Athlon XP) fixes the issue?