That buzzing is interference. The more gain a preset uses, the more that interference gets amplified. The more the interference gets amplified, the louder the buzzing. "Real" amps work that way, too.I turned on my FX 3 last night, and the first thing I noticed was that some of the factory presets had no buzzing, and some did. The ones that have more buzzing, have a louder sound profile when playing. Makes sense I guess.
What happens when you unplug the cable from both ends?When the guitar is plugged in, the buzzing is a higher pitched buzz. If I unplug the cable from the guitar only, the buzz is more a of lower-pitched hum. So it is not just the guitar, but the cable also.
All of the presets are buzz-free when there's no source of interference in the room. Best to eliminate the source of the interference, if you can. If you can't, use the noise gate on the input block.I would think that someone who has created a buzz-free preset could enlighten us on how to not have buzzing?!