That is a slick amp, and nice 4 tube approach.
I was going to ask the dumb question, 6bm8 as a triode and a pentode. While slap my hand. That 6bm8 is pentode-triode tube. not a pentode slumming as a triode.
Any ideas or numbers on the transformers?
Here is a link.http://www.superseventeen.com/goodsell-black-line/unibox-10---black-line.html
These are great guys. They show you the gut shots along with the transformers used. They are using a Warehouse 12 speaker based on the C12Q. They are not secretive in the amps they build. Like Barry told me, they retail for $1400 almost at the better music stores around Atlanta. Most of these shops will knock off some bucks. He told me it cost him $480 in parts to build and that includes the cab but no speaker. He likes Classictone OT and edcor and heybour PT's on smaller amps.
You can see in the gut shots the caps used. If you want, you can shoot them an email and they will tell you what they changed. It is really a nice sounding amp. They have a line of amps, but the 17 is the best all around IMO. This one just has a great reverb and tremolo and is very pleasant when cranked. Sort of like a Princeton reverb meets a Vox AC-10.
What is weird is in the 70's we made fun of Univox as being junk.
It's pretty straight forward, you can look at the photos of the gut shots and build it.
No, I do not work for them. They have just helped me out on many occasions with parts I needed now.