How does it sound with an RCA to phono plug conversion?

If by "phono plug" you're referring to a stereo 1/8" mini jack, that's not a conversion. That's just the wiring that's used for the sound card's line input. The empeg comes bundled with the correct cable to make this connection directly. In that case, it's the empeg's line out to the sound card's line in. That's the exact kind of connection that it was intended to make, so it sounds fine.

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Tony Fabris