Stereo Tool

Good morning!

I'm really hoping someone can help me:

I have a Pro-ject Debut Carbon vinyl turntable I have USB'd to my desktop (Win7) via a phono amp. What I *want* to do is have Stereo Tool work its magic on my vinyl playback (through my Harman/Kardon SoundStick III 2.1 speakers).

My turntable shows up as "Turntable 2-USB Audio CODEC" in 'Recording' devices in Sound.
When I open ST as well, Sound/Mixer gives another volume slider for ST. However, the music plays "twice" concurrently, first (of course) the sound from the turntable playing, and then it plays 'again' from ST, albeit with a very slight delay. I've tried muting or lowering the volume from the "Turntable" recording device, but that just cuts off the input to ST and instead ST 'plays' the last small portion of sound on a jilted repeat.

How do I make this work? I want to listen to the ST-sound, rather than the 'raw turntable output' if you will.

I use my motherboard's on-board sound: ASUSTeK Computer INC. P8Z68-V (LGA1155)
Realtek High Definition Audio

Thank you in advance for any pertinent assistance anyone can offer.