It uses the Stevens & Billington TX-102 autoformers, the same as found in the unobtainium Bent Noh preamps.
Aren't the S&B TX-102s transformers with two seperate windings? I'm not totally sure, but it seems to imply that on
http://www.stevens-billington.co.uk/page102.htm'>S&B's site
I can also vouch for how clean/transparent these things are. Both DiyHiFi or Bent are the same design, but John at Bent supplies a different wire to S&B so it is a bit different in the end. Bent's new product looks interesting, but of course it depends on your timetable since its not totally ready yet.
If you are willing to DIY totally without a kit then you might ask John if you can buy a couple of his txs. He may not be able to sell them still, but before they were the pretty much the same price as DiyHiFi and you don't have overseas shipping if you are in NA.
Another nice thing about a transformer like this is that you can end up with a pseudo balanced signal out the back end even if fed single ended RCA.