Good to see you still working on projects like this Billy!

My brother, dad, and I made a project similar to this as a Fathers Day activity a couple years ago. Used black walnut for the neck, with a simple oil finish. No frets. My dad and brother made 3-string guitars, and I made a 1-string bass (34" scale with a single flatwound string and a humbucker pickup).

As some of you might know, I do a fair bit of work on tube amps myself - I've built some tube gear from scratch too. I don't know much about 6SQ7 or 6SL7 though. Sadly I'm young enough that my electronics courses in college barely even taught us transistors, instead focusing on op-amps and other IC's, so all my tube knowledge is just stuff I've picked up through working on guitar amps and the odd tube studio gear.

Gordon's correct about the DC voltage - if you have a 270v transformer and a 5Y3GT, you'll probably get around 330v DC at the output - though this is variable depending on load, wall voltage, and other factors.

How I got to this number:
AC voltage multiplied by 1.414: 270 x 1.414 = 381
The 5Y3GT datasheet tells me there's a 50v drop with a 125ma load

I agree that tubes certainly add character to guitar, however the biggest factor is the speaker, not the tubes. Tubes aren't even second place, the output transformer is! When I'm recording at home, I mostly use guitar amp plugins (in particular there are a couple plugins that let you copy your own amp using machine learning), however I always get the most "real" sounding results when I re-amp through a real speaker, which I usually use a solid state amp for. YMMV though.

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