9v Power adapter question...

I bought a 9v power adapter off ebay for a new guitar pedal I purchased. Unfortunately the guy I bought it from posted incorrect pictures and I ended up with a smaller "head" (I guess) then what my pedal accepts.

Basically I have this



and what I'm wondering is if I can cut a correct sized "head" off another power adapter (12v) and wire it to the 9v adapter, so I will achieve this

 

It is hard to tell with this kind of thing as it can be risky. Do you have 2 other cheap things the same head or similar head that you can do a test run on before you do it to this. Try it with that and then do it with that one. Just for safety.

 

You can try it but I'd recommend maybe just getting the one you need from a store like Radioshack if they are near you.