It’s time for the leap of faith. Having tested the 814 in triode mode, I will proceed now to upgrade my 4-65a SE amplifier and replace output valve for the 814. To ensure it can withstand the 540V in the anode, the remaining grids are all tied together through a resistor to the anode. All grids and anode are fitted with ferrite beads as well. A pair of UF4007 in series are placed to protect the Output Transformer in case load is accidentally disconnected.
I added to the UX-5 socket a small bar to place two turrets to provide the anode (top connector), the strapped grid connections through the wire-wound resistor and the pair of UF4007 diodes.
Given that the 814 will run @ 540V / 100mA, I will only need to adjust the Rod Coleman regulators to set current down to 3.25A after replacing the raw filament transformers, as the 814 are 10V instead of 6V filaments of the 4-65a.
Minor DC adjustment will be required on the driver circuit via the gyrator load, so can easily implement this new amplifier.
Stay tuned…
Dear Bartola Vacuum Tubing Team
The data sheet of the 814 does not publish data on how to work this valve in audio frequency, but observing the sheet of 828 if I have observed that it has a difference of 20 to 25% less power with respect to the set of values class C telephony you can see that physically they are very similar
The 828 promises 385 Watts of output and the 814 can estimate about 280 Watt
HI Pablo, these valves weren’t designed to operate in Class A.