I'm using the Radial BigShot ABY. With the right combination of the pedal's ground lift and phase settings, I'm not getting any unwanted noise. Guitar to the ABY pedal. "A" line to Line6 Spider IV 75; "B" line is the RockSmith USB cable to PC. In Rocksmith audio settings, Player1 guitar volume is turned down as far as it goes, so the guitar is only coming out of the amp. I use the Spider IV presets to try and match the tone of the song I'm playing in Rocksmith. It works pretty well. Pink Floyd - Shine on You Crazy Diamond preset, Nirvana - In Bloom, etc. Works pretty good. I just added the Line6 FBV Shortboard, so I can switch tones in the middle of a song when needed (still working on that). Playing through a real Amp has definitely improved my play. If you are playing like crap, you can really hear it, but also very satisfying when you are nailing it!