I have never used split rail power supplies before and I am working on something for a friend please let me know if this will work:
(http://i58.tinypic.com/awrdle.jpg)
its a toggle between the 9v and 18v taps of the charge pump - the resistors are an attempt at blocking a pop when switched but I don't know if they are necessary or if they will not work at all
thanks
I've no idea if this is actually important here bcause I haven't seen the rest of the circuit or the power supply, but a warning flag did go up. If the switch is a make-before-break or if there is a big cap after the switch, then switching from 18V to 9V could put an 18V spike onto the 9V input line. I'd do something to protect against that possibility like using an inline 1N5817 on the power supply input.
You might also want to check the path back to the charge pump and make sure that the output pin of the charge pump is protected against an unwanted 9V spike when switching the other direction.
thanks, good thoughts - re:context - Jfet gain stage