The classic 807 beam tetrode designated as a military valve. The ceramic base offers better insulation in humid conditions or at altitude. The exact details of what makes the N variant of the ATS25 have not yet been found. Both the ATS25 and ATS25N have ceramic base caps.
The parameters given are for single ended use. When used in a class AB1 as a push pull pair with 600 volts on the anode an output power of 65 Watts was normal.
The only visible difference is the anode shape.
The ceramic base. The connecting leads are seen to be soldered to the ends of the five pins.
The top mica with the grid shield.
The classic envelope is 51 mm in diameter, and excluding the UX5 base pins is 130 mm tall.
