I just bought brand new speakers, and everything is hooked up correctly, but I get a scratchy background noise- I connected my speakers to a separate CD player and they work perfectly, without the scratchiness, so it's not the speakers. Could I need a new sound card, or is there something else I can check?
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It could be interference from another card adjacent to the sound card. Pop open the case and see if there's any spare PCI slots so you can put the sound card in a different slot so it's further away from other cards.