Where to take a live for a speedo convertor
 

I've bought a replacement speedo convertor, as mine has been on the blink.

To rule out the possibility that the live was the problem rather than the convertor, I'd like to take power from another location. Where's best in this region?

My existing one is wired into something behind/below the steering column with an extended wire. I'm pretty sure I should be able to tap into something within the speedo cluster loom?!

Car is a 2005 STI.

Cheers