Source is a turntable running through the preamp only, of my Pioneer SX950 stereo receiver. I have a new Behringer external USB sound card with stereo in/out RCA jacks. When I monitor the source I have stereo. But when I roll balance all the way left both channels of Sound Forge go away. When I roll balance all the way right both channels stay and they are identical. The finished recording is not stereo. Left channel missing. Thoughts? Thanks guys.