You can use two soundcards (I have with recording musical instruments) but you can't output both cards to the same set of speakers. If you have headphones (depending on your sound card's capabilities) you would have to set the sound card you want to use with your head phones to output to that device. If you have speakers, then you would have to set the other sound card to use the speakers. Normally that is done through the Playback settings in windows.(right click on your speaker icon and select it) Of course like I said, this will only work if your hardware supports it. Most cheap sound cards don't have that capability.
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