On Thu, Oct 8, 2020 at 10:38 AM David Gow <6146guy at gmail.com> wrote: > > For actual Eimac tubes the Eima DATA sheet shows much greater efficiency and usable power with 4000 volts on the plates. Where are you looking? At the characteristic curves? There's nothing for 4KV in typical operation; just max ratings. 73 Rob K5UJ