CH2 (dirty) popping noise??

[MassiveBoogers]

Does anyone else have this problem or had it in the past? 1 and 3 are fine but channel 2 almost always has a loud "POP" (almost typed "poop", which wouldn't have been accurate, heh) when switching to and from, which sucks because I would like to use it a lot more often..

 

[boss4]

Old thread (actually mine):
http://forum.grailtone.com/viewtopic.php?f=24&t=51948
The thing is if it makes the "pop" every time you press the 2ch button or if it only makes one time after you switch on the amp. If is the first, something is not right; if is the second, there's nothing wrong and you can hit the 2ch button right after switch the standby so you dont have to listen that loud "pop".