9v / 18 switching for grapevine/ faultline

[soldersqueeze]

I'm looking to build these projects up and I've seen some people include switching to choose between 9 and 18v. I can understand preferring one over the other but how useful is the ability to change them on the fly?
While I'm on the subject, would it be practical run both these effects from one road rage using two dpdt switches to change between voltages like this-

?

Any advice appreciated

[madbean]

I don,t know how practical it is but you don't need to use that kind of switch. You only need to switch the 'hot' supply, not ground. So, an on/on spdt with 9v on one lug and 18v on the other is what you should use. You can have one switch for both or one for each.