I know very little of electronics and how amps are built, so please excuse any ignorance in the post. I've got an older Fender 80w, 4 channel P.A. that has a handy little switch in the back which allows me to choose between 110v and 220v. It's simple, and very handy for me, as I have traveled between the U.S. and Greece, bringing my equipment with me, and allowing me to use it in both countries. Of course, there are other heads, amps etc. that also have this feature. More often that not, though, this feature is not built in. My question is: How difficult would it be to take a bass head that does not have this feature, open it up and convert it to provide this feature? I'm sure each individual case is different but, generally speaking, for someone that knows what they're doing, would it be possible and cost effective to convert a bass head to be switchable between 110v and 220v? Thanks!