Hello there! So the thing is in the topic and here're some details.
Sound card is CT1600 and it's connected via riser.
I've tried two games on it, Wolf3D and Doom v1.9 and both of them freeze with SFX turned on (run well if using sound card just for music or not using at all).
Sound Blaster has been checked on another 486 machine and there it works flawlessly with the same games.
Power supply voltages seem to be O.K.
Riser is primitive and has no ICs. All of the electrolytic capacitors have been replaced with new ones last year (after floppy drive faults).

Any thoughts?

Thanks in advance!