Amp switching pop. How to eliminate?

[Morocotopo]

Hi fellow DIYers, I have an amp-related question, but I believe someone here might be able to help:
I made this thing, first DIY amp, circuit is a hybrid of some other circuits.

http://i68.photobucket.com/albums/i5/Morocotuco/Dluxe-Princess-Mk1-rev-24.jpg

It´s working OK, but when I switch the extra gain stage in and out, I get a pop. Not a really loud one, but there nonetheless. I´d like to eliminate it. Does anyone have any idea about how to do it? I could live with the pop, since it´s not an on-the-fly switch (not a foot switch), but...
Any help appreciated.

[Ripthorn]

What are you using for a switch?  A dpdt stomp will be different from a relay and both will be different from an optocoupler.