I originally got the PRS connector and it sounded terrible with IK-Multimedia Amplitube as well as the new Ampkit apps on my iPod touch. It definitely had issues with the input impedance mismatch. I recently got the Peavey/Ampkit iLink interface and it is a drastic improvement. The iLink is actually active and runs on 2 AAA cells it solves the impedance and feedback like problems of the PRS interface (I have not tried the iRig interface as they were very slow on delivery). I then went back and tried the PRS interface with both a compressor and a clean boost pedal set very clean and that seemed to solve a lot of problems. I believe that incorporating an opamp IC or a discrete transistor circuit into the interface would help immensely with the overall sound quality.