Hi I'm building a PCB board at the moment with a 3PDT attached. I was wondering if I actually need a d.c jack attached to the power?
This post should be in the "Build Your Own Stompbox" area, but to answer your question, if your circuit draws low enough current to have decent battery life from a 9 volt battery, then no you don't necessarily need a DC power jack. Many people run the ground through the input jack in such a case so that the battery doesn't drain if no cable is plugged into the input. The power is switched in that way rather than the 3PDT to avoid a gigantic turn on/off pop. I don't have a schematic to refer you to at the moment.
Hey thanks that was helpful information :)