The Defy 7 has a very high input impedance, so its not really particular about what preamp you mate with it, and not too picky about interconnects either.
With my Defy, I enjoy great sound with a Jadis DPL, and previously, a Levinson 38S.
Your main concern with the Defy 7 is to keep well matched, properly biased output tubes in it. I can't stress this point enough. I've had good luck with the new Tungsol 6550s, and Mullard EL34s. The 6550s are easier to bias to the recommended 4-5volts. The EL34s sound great, cost less, but obviously don't have as much output.
If you're trying to keep cost down, keep in mind you are pretty much on your own when it comes to service. If you're good with a soldering iron, its not too much trouble.
For a wiring diagram, you can contact Jadis directly. They sent one to me, although, its a bit low rez.
In spite of the difficulties I've had with mine, it still is one of the best sounding amps I've ever heard. That's why I've continued to put up with it for twelve years.
I also recommend finding something like a Heathkit TT-1 tube tester, if you plan on sticking with tubes.
One more thing. DO NOT, EVER, REPLACE ONLY THE OUTPUT PROTECTION FUSES AND NOT THE TUBES AS WELL. If you follow this advice, you should be fine.
