OK, just for the records seems like I solved the POP problem: I had too many wires running around, so I've rebuilt the unit with a new PCB with the switch (and all the pots) mounted directly on it, then I've replaced all of the ceramic caps with film ones, but the pops were still there, though the sound and noise performance have increased dramatically.
As a last attempt I've sprayed some contact cleaner directly at the base of the switch lever, where the little sphere is: the switch is completely closed but not sealed, and apparently that stuff has enough penetrating power as to get inside of it from there.
A few on-off cycling and voilĂ ! the pops are gone!
As a last attempt I've sprayed some contact cleaner directly at the base of the switch lever, where the little sphere is: the switch is completely closed but not sealed, and apparently that stuff has enough penetrating power as to get inside of it from there.
A few on-off cycling and voilĂ ! the pops are gone!