The change in sound that you notice when you use a noise gate is produced by the elimination of unwanted frequencies... Noise gates will slightly alter the sound no matter what because it's clipping frequencies that are commonly known as "noise" frequencies. No noise gate is absolutely 100 % efficient. However, the Boss noise gates are probably some of the higher quality gates. I don't have a noise gate, because I use a PODxt LIVE and a GENX2 which both have gate features on them. When it comes to choosing a gate, definitely take your axe to a guitar store and hook into all the gates you're looking at. Different pickups generate different frequencies and operate at different levels. A gate that is good for one guys guitar may not be the best one for you to use. Even though all noise gates have different settings to adapt to any amount of frequencies... the settings may not give your set-up the same results as the other guy. So just try them out and see what works for you.