DON'T connect J4 to mic input on soundcard...
I realize this is an old thread, but for those who haven't figured it out by now, DON'T connect the J4 input to the sound card mic input. It sounds like the original poster did that. J4 is for an external microphone. It is not meant to connect to the sound card's mic input. Usually you need a measurement mic run into a mixer or phantom power device. Then you run a line-out from that device to the J4 on the jig.
Just thought I'd post in case someone comes across this old thread and is confused about the mic jack vs. J4 on the jig.
And as others mentioned, get those record levels set properly. Set your receiver volume to 1 or 2, and the Windows record mixer line-in all the way up. As mentioned in setup routines, record a sine wave and monitor the left and right "in.l" and "in.r" graphs. Change the Windows mixer sound level until sine waves don't clip. As a side note, sine waves should measure around +16k/-16k. MLS signals will be about +/-22k at this level. Click "view-vu meter" on the menu to monitor this.
Good luck to all.