• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Looking for high-voltage tubes

Hi Jan,
very interesting project... I also thought already about how to build such an amp... I would try a 4-125A (QB3/300). Max. plate voltage for RF power amplification should not exceed 3 kV (datasheet...), but from its construction its plate can take a lot more.... Max. screen voltage up to 600V, with such high plate potentials I would rather go quite a bit lower, 200-300V. Graphite plate and very rugged construction, so I think this would be a good beginning at least... But how do you plan to realize the plate resistances? Resistors, chokes?
In this way I also operated an EL81 with up to 1,2 kV DC plate voltage (and 70V screen) as a regulator tube for a power supply, which could be set from 800V to 1,2 kV output voltage using an EL519 as pass tube.
If it should be a triode, I would eventually try the former colour TV HV shunt regulator triodes like the PD500..... Maybe two or three of them in parallel?
all the best
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6HZ5 6000V 30W 300mA pk

I believe that it is to limit the Pa as they are HV regulator tubes, but there are no charts
on lower voltages.
I doubt that you cold make a wire thin enough to fuse at 1,5 or even 25ma and have it survive
as a lead in wire in a tube.
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I am wondering, those HV reg tubes with Va up to 25kV with Ia(max) 1.5mA.
Would they break if Ia was 25mA peak?

Look at the heater power. 6BK4 6.3V 0.2 Amp , smaller than a 12AX7/ECC83
I have a 6BK4 here, and the cathode is miniscule.
That PD500 looks better though. 7.3V 0.3 Amp

The PL519 looks better than the 6HZ5 for continuous HV, since it has a plate cap. The Compactron socket (only) of the 6HZ5 would probably break down with continuous HV, unless you submerge the socket in silicone oil.
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