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What is the model number of the Bush system? Does it have a DVD player or any type of central unit?
If not, does the sub have a "digital" input jack? If not, then at most, all it will do is amplify the various feeds it gets from your sound card. To do that you'll need 3 cables that have a mini-headphone jack on one end and two rca plugs on the other. Hook these up from the various outputs (from the Realtek)to the corresponding inputs on the sub. Wire up the speakers. Then go to the computer sound set up and tell it to output 5.1 surround. Try
HERE for more info on the Realtek
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