Hey-Hey!!!,
The schematic will have to be a pen and paper deal. I am not skilled with the Electronic methods. Email me and I'll draw it up for you( probably make some copies too, or scan it and pass it around...Own design is an interesting concept. I did not see this exact thing elsewhere in the exact form I will provide you( or anybody who asks ) with. I have build a few linestages, and will build a few more before I am done. This is about as simple as I think it can be done and still deliver 'the goods'.
If you are going to go DC on the filaments, the Hammond 261C6, E6, and G6 are all capable of running the rectifier, and are a bit cheaper.
regards,
Douglas