I have just completed a Hudson Broadcast (which is just awsome!!!). It comes in a 9 volt and a 24 volt version and I opted for the 9 volt version, because I have an external voltage doubler and like the flexibility.
Messing around with the Broadcast, I have been switching back and forth between 9 and 8 volts. Both have qualities I really like. That got me thinking. Is it possible to build a charge pump that can toggle between 9, 18 and 24 volts using a three position toggle switch?
I think it would make a really cool addition to the Broadcast (and probably a lot of other pedals)
As far as precise voltages, typically you don't get exactly the number, sometimes it's a little more or a little less. As long as it's close enough your good. Take for instance the mini model t i made. I have a board with a transformer that converts 120/220VAC to 24VDC. I don't get 24VDC on the dot, it actually reads out 24.52VDC. If I was getting something like 20VDC it would be a problem.
The doubler I built from Harald sabro gives me 9.42 and 16.74 volts It certainly makes an audible difference to the clarity and headroom, like it a lot.