What are you using it for? I'm not familiar with Guitar Rig. Is it for recording? If so, you shouldn't need a stereo converter, it's a mono signal - providing you're only recording from one source at a time, of course.
yeah the program is so I can plug my guitar in my comp and then record it on the computer with guitar rig..but is that the right jack?
i don't have guitar rig or know anything about it, but if the input on the processor is 1/8 inch, then it should be fine

maybe wait and see if anyone else can confirm this, just incase..
He's is asking for a USB soundcard (does not need a jack input) under 40 dollars which will work ok on guitar.

Do any of you have experience with a such usb soundcard?