Warren, I had always heard that changing out the tubes on the SET40 for NOS made a big difference, especially on the input side. I never had the chance and am now even regretting more.
I've been using a Blue Circle BC21 preamp with various NOS for years and can definitely say that WWII era 6SN7/VT231s are a huge improvement over stock. Incidentally, I was using this preamp with the SET40. The 6SN7 as you may know creates a rounder, fuller sound. I had always enjoyed this in front of solid state amps, but was very happy to find it worked well with the SET40. I can only imagine how well the SEP1 synergizes with the SET40. Must be great!
Have you swapped out the stock 845s? At least, unlike with 300Bs, you don't need to be the creators of YouTube to be able to afford a little 845 experimentation. Woohoo!
