Found this thread while researching whether the HX Effects has an input buffer. Wish Line6 would provide a schematic diagram to confirm like TC and BOSS do with their Multi FX. However judging by the high frequency boost described here I think I have the answer.
@dannywmusic Check out the "Do I need a Buffer??" video by JustNickMusic on YouTube. It explains well how the buffering changes the tone and how long cable runs act like a high-pass filter. When you engage the HX, in a way you're shortening the cable run reducing how much high-frequencies are cut off.
