I'm at a little trouble trying to figure out what is the best topology to choose.

Is it possible to use a non isolated boost converter to step it up that much or is there a practical limit to the step up ratio of that topology?

I have built and tested the converter described on this page.

It's a really clever design, however i would like to design my own converter!!

http://diyaudioprojects.com/Tubes/12AX7_Preamp/index.htm

Anybody got any suggestions?

thanks in advance, steve.