Power supplies

Is it possible to wire 2 1-spot 9v adaptors in series for 18v?
I know the obvious answer is a dedicated 18V PS (I have one); however all my pedals are 9V except for one (old Cool Cat) which is 18V.

For reasons of elegance I would like to install 2 One Spots on my pedal board, especially since I travel to Europe (220V) and the One Spot is a switching PS which will work on 117 to 200VAC.

From Visual Sound's FAQ:

Can I "Y" connect 2 of the daisy chain power plugs on the 1 Spot to deliver 18V to a pedal?

There is no way to get 18V from a single 9V adapter... not even the Godlyke one or the 1 SPOT. Think of it this way... adapters are really like batteries in that they output DC voltage via a positive wire and a negative wire. With batteries, the voltage increases when you run them in series (i.e. When you line up 2 C size batteries in a flashlight, each battery is 1.5V, but when combined it's 3V). This is because you are running them end to end, negative to positive. You can't do that with an adapter. You would need two adapters, taking the negative wire from one and the positive wire from the other, tie them together, then take the other wires (positive and negative) and connect them to whatever you want to power.

The point of this is that you need *separate* 9V power sources to combine together to make 18V. Two separate plugs on a daisy-chain cable is not two separate power sources because they're both coming off the same wires. Now, you could get two 1SPOT's and create a Y cable to join them together and make 18V, but that's a lot of trouble and expense to go through when you can just get an 18V wall-wart adapter from Dunlop (or others) to do the same job. Lastly, IMHO, overdrive pedals sound brittle (overly bright) when powered with18V, *and* you're pushing the maximum voltage rating of the op-amps so the lifespan of your pedal may be very reduced.


http://www.visualsound.net/index.php/resources/faq/#6

From Visual Sound's FAQ:




http://www.visualsound.net/index.php/resources/faq/#6

Thank you Udister; I had read that FAQ. I just wondered if any one had done it. I did a schematic and it looks like there will be ground (earth) conflicts if I want to use both the 9v outputs and the resulting 18V output; I'm not sure if the pedals' signal grounds are shared with power ground. I guess some experimentation is in order.