• 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

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#24
I would use 813's in a push-pull configuration. 50 watts of filament power is a small thing for the light they give off on display.
Of course the issue is you are a dutchman! Or are you channeling an American audiophile?

The tubes are easy to find, the sockets a bit more bother,
 
#27
simon7000 said:
I would use 813's in a push-pull configuration. 50 watts of filament power is a small thing for the light they give off on display.
Of course the issue is you are a dutchman! Or are you channeling an American audiophile?

The tubes are easy to find, the sockets a bit more bother,
Click to expand...
Hi Ed, I currently have an amp with 4400V total supply and a cascode amp producing like 1500Vrms but that cannot fully drive the ESL63's.
I want to go to 2500Vrms or so. These ESLs are balanced drive so I need two out-of-phase outputs each swinging like 7000V.
Using the current cascode but replacing the top tube with n inductance would do it.
Right now I get by with 30W dissipation of the 6HS5.

Jan
 
#28
Hi Jan,

by far the favourite for this job will be a 212E - probably a Chinese replica like: https://www.eectech.store/products/...equivalent-to-ml-212e-we212-hifi-tubes-we-212

It ain't cheap but has the power and can handle the voltages involved. Can be driven by a single 6HS5 to get the desired gain. PM me and I will share a schematic as to the usage I have in mind. Too similar to a commercial product to post here. 🙂
 
#30
jan.didden said:
I'm looking for a high voltage tube for my next gen ESL direct drive amp.
Basically Va(max) at least 6500V, with a Pa (max) of at least 50W.
Everything else is negotiable but preferable not one that requires me to take out a 2nd morgage ...

Jan
Click to expand...

If you look at the design maximum ratings rather than the design centre ratings and forget that the specified voltage is a peak value, a single Philips PL519 is already quite close: 8 kV and 45 W.
 
#32
jan.didden said:
Question again. If I look at say an 813, the max Va in the various modes is 2250 or 2500 V.
Yet, that is a DC spec, and if I use a SE choke loaded stage with say 2500V B+ (DC), the anode swings between close to zero and almost 5000V.
Does that then not violate the Va spec?

Jan
Click to expand...
It does not. It's pretty normal as all power tubes are inductively loaded and routinely used at or close to max DC voltage for better efficiency. Sometimes even a bit beyond....
It is very important that you comply with screen grid limitations (both DC voltage and power dissipation from DC all the way to max modulation, especially if not Class A) with pentodes.
 
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#35
I would look at the 833a triode. It's 3KV and 300W plate dissipation with natural air cooling in AF application. However filament power is 100VA (10V @10A). MagZ in this forum made a nice SE amp and has a long thread with lots of info and pics (the title of the thread should be "the middle life crisis" or something like that).
 
#36
MarcelvdG said:
If you look at the design maximum ratings rather than the design centre ratings and forget that the specified voltage is a peak value, a single Philips PL519 is already quite close: 8 kV and 45 W.
Click to expand...
PL519’s aren’t designed to conduct low current (at high dissipation) at 8kV. They are only designed to be completely off at that high a voltage. High voltage shunt regulator types are more suited to high voltage amplifier duty.
 
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#37
If you would consider pentodes the Eimac 4E27A/5-125B is about the right size and only 37.5W filament, and dirt cheap. All of these Eimacs are gettered by coatings on the anodes, and need to run somewhat red-plated (no barium getters), and with heat radiators at the glass-to-metal seals, but are made for high voltages.

All good fortune,
Chris
 
#40
Jan,

You can do what Crown calls a grounded bridge. You use two bridged amplifiers with separate floating power supplies. Then you can connect the bridged amplifiers in series. As a single bridged amplifier can effectively put twice the power supply voltage across a load, floating bridged two pairs will get you to almost four times the rail voltage.

Oh by the way keep your nose and all you other body parts well out of the way! Just a suggestion!

ES
 
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