Be careful, this capacitor is too big!
You can disturb power-up voltage sequence and destroy
you comp! And it is not the solution!!
Check, first of all, that your cable between soundcard and
amplifier properly shielded to PC ground, check that PC
and amplifier have the same signal ground, common grounding
via 220/110 outlet is not enough, may be you'll need even
disconnect outlet ground from amplifier and stay with
signal ground only, that amplifier get from sound card.