the closest answer would be any card without a built-in amplifier. use the "line out" instead of the "spkr out", or bypass the amp thru the jumpers. this turns the single output port from "spkr" to "line" out. set mixer volume of the card to only 50% to 70% and do the loudness controls at the amp side. if the noise persists, it could be the external amp you're using, or bad cables.