? re: power supplies + voltage doubling

[stuartgsmith]

Is it possible to wire two 9V outputs from a power supply (a Voodoo Labs Pedal Power 2 in this case) in series, in order to achieve a single 18V output?  Could this harm the power supply?

Diagram below:

[niftydog]

ok, what you've drawn is not "in series", and you need to read the manual for your power supply!

I beleive it works like this; Hook one outputs +ve to the second outputs -ve. Then, between the first outputs -ve and the second outputs +ve, you'll have 18VDC.

I tell all my friends to read the manual before they ask me a question about electronic gadgets... do you think any of them listen to me!??!  :cry:

[stuartgsmith]

Hmm yes RTFM as they say... :oops:  
Bad diagram, I guess, but I get the + to -, - to + wiring concept.
Thanks!

[R.G.]

Is it possible to wire two 9V outputs from a power supply (a Voodoo Labs Pedal Power 2 in this case) in series, in order to achieve a single 18V output?

It is possible although unlikely.

Let me explain. Most multi-output power supplies are simply single power supplies with many parallel output jacks. That is, all the - outputs are wired together and all the + outputs are wired together inside the box. Obviously, you cannot stack the outputs on a power supply like this without simply shorting out the innards.

Some multi power supplies are independently regulated per output. That means that they share only a common ground. However, it still shorts the one output to the common ground if you try to stack them.

Only a few, quite expensive multi power supplies have truly independent outputs. See the article "The Spyder Power Supply" at GEO for how these work. These kinds of power supplies CAN be successfullly stacked for 18V, or +/-9V, or -9V or -18V. There is no internal connection between outputs.

How can you tell? Get out your digital multimeter, set it to ohms, and measure the resistance between (-) leads. If there is any resistance under 100K between leads, especially if it's a dead short, then you cannot stack the outputs. Don't have a DMM? Either go get one (they can be had for under $20 every day, often less than $5) and learn to use it, or give up on ever doing any electronics messing about.

Could this harm the power supply?

Some poorly set up power supplies, yes. Independent output supplies like the Spyder, no.

Ted Weber sells a tranformer ideal for making a Spyder on the webervst.com web site. It's about $15, and a bargain unless you *like* multiple transformers or winding your own.

[stuartgsmith]

Interesting.  

From the Pedal Power manual (which I have now f'ing read):

Can I power my pedal which requires 18V (uses two 9V batteries)?

Yes. Because the Pedal Power’s outputs are individually isolated, you can wire two of them in series for 18V. Be sure to observe proper polarity. Digital Music can provide you with a custom cable to do this.

So it is possible with the Pedal Power, but maybe not with other power supplies.  Good to know.