Been pondering for a long time about building AC4. The datasheets for the 2 pentodes were copied. Put together & the AC4 was born. My approach would be the same. It worked for Vox it should work for me. No need to re-invent the wheel. I think I've found all the drawing errors & mods. EF86 seems to have noise problems. No experience with Vox gear. Any thoughts would be appreciated. Many thanks.