5F1 transformers, tubes, and headroom - how and what to measure

JJ 5y3 usually does well at getting the voltage as low as you can hope, but I would still expect 380v-390v range B+ probably. It will still probably sound great, but in my experience, it will probably just have a harder "edge" to the tone/notes while the lower vintage schematic level seems to have a fatter tone and a bit softer/warmer sounding. If it's too clean, raise the 22k NFB resistor to 37k-56k range and it will gain some dirt.

 

Since you already spent the MM-money, I’d build the amp stock and see what happens. You could possibly also use an NOS 5Y3 to drop volts; Jason knows a ton so his JJ there may be perfect. And I’d also start with JJ 6V6s — 14W rating is very conservative, IOW, they can handle high voltage.

Before we get into voltage measurement (fairly simple), you asking makes me ask : Do you know how to drain the fiiter caps before working on the amp? Better yet, do your plans include a bleed resistor to do it automatically?

 

Yep. 100k 2W is pretty standard.

 

No reason not too. However, I used to always build my 5f2a's with a 3 way switch, but as most people on here will tell you, you'll eventually find one place you're happy & leave it there. It may be worth rigging it temporary and not drill any extra holes and just experiment some. Upper 30k range with an 8 ohm speaker equates roughly to what stock value is with a 4 ohm speaker. I like 56K with an 8 ohm, but it definitely gets the good dirt, kinda 5e3-style at that point. So, if you are wanting a cleaner amp, you probably don't want higher than upper 30k range at most. A little more can add some nice top end bite, but by 56k and above it's going to be short on headroom.