No luck so far but made some observations while testing wolfenstein 3D with CT1600:
1) /M switch (master volume) is required. Without it, the other parameters do nothing. /M must be at least 8. With 7 or less, FM sounds are off and digital voices are very quiet (I kept VOC and FM at 12). Setting /M to 8, 9, 12 or 15 do not matter, left channel is always mute.
2) Running test-sbp and testing the sounds fixes the card so everything sounds fine. I think it initializes the card so that sbp-set would have never been set in the first place.
3) When sbp-set mutes left channel, it must be fixed with the sbp-set /R or by the test-sbp. Simply rebooting won't help. Power must be completely turned off.

I tried to configure the card from A220/I7/D1 to A240/I5/D3 but no change. I even tried the DMACTL jumper but as expected it did nothing. Then I tried to disable internal cache (this computer has 486DX 25MHz so it should not be too fast) but no change.

I actually have 5,25" driver disks for this CT1600 card (one HD + one DD disk) so I copied them to 3,5" disks on another computer. Those 100% correct drivers did not help either. In fact the SBP-SET was the same version I've already tried.

I need to try the card on another computer next. If SBP-SET works there then I suspect there is a compatibility problem with Headland shasta chipset that this computer has. One thing I noticed is that both the CT1330A and CT1600 have v3.01 DSP, CT1345 and CT1336 chips.

I tested the CT1600 on another computer (Cyrix 486DLC-40 with Opti 495sx chipset). SBP-SET works just fine. So it looks like there is some sort of compatibility problem with Headland Shasta chipset. The Copam with Headland and 486DX-25 feels a lot faster than this Cyrix DLC-40 so maybe the headland would need some wait states. There just wasn't any wait state or ISA related in the bios setup.