issue on sound card

i have this old sound card (sb16) that uses an isa slot. when i first bought my pc, it was working fine. the speakers sounded great. 2 years ago, i upgraded my pc but to my dismay, i thought the soundcard is not anymore compatible with the the new system. it’s still running anyway but i cant use the “speakers out” anymore with my conventional unamplified speakers. it only works with amplified speakers. the board im using right now does not have onboard sound so i think there is no conflict in any manner. im confused on what seems to be the problem. im running windows 98se. will anybody help me?