Looking for high-voltage tubes

[jan.didden]

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

 

[EUVL]

I am sure you have seen this :
https://www.reddit.com/r/highvoltage/comments/13ds11a

Patrick

 

[ulibub]

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
Uli
@tubeampuli

 

[amplidude]

Interesting..
If you need high voltage transformer-rectifier-capacitor Look at this Danish add.
https://ham.brugtgrej.dk/annonce/191702
Heavy stuff

 

[jan.didden]

I am sure you have seen this :
https://www.reddit.com/r/highvoltage/comments/13ds11a

Patrick

No I hadn't Patrick. Thanks for the heads-up!

Jan

 

[jan.didden]

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

 

[petertub]

HOW ABOUT 304TL ? I have at least 2 ( maybe 4 )
LIKE DA42 with top plate connector. I also have 2 meanwell power supplies to power the filaments.

 

[RJM1]

6BK4? only 25W but 27KV, two in parallel?
We used 4 of them in paralell for load testing 3ma 33KV power supplies for video projectors.
Lots of lead tape on that box.

 

[smoking-amp]

6HZ5 6000V 30W 300mA pk

 

[jan.didden]

That's an interesting tube.

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?
Is that 1.5mA a max because of the brittle fine wire/construction or is it 1.5mA to limit the Pa with those 25kV anode voltages?

Jan

 

[MarcelvdG]

Two PL519's in parallel? They are actually specified for high voltage peaks rather than continuous high voltages, but hopefully they will survive. You could also ask @Lampie519 , he has used DIY direct-drive amplifiers for years.

 

[RJM1]

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.

 

[smoking-amp]

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.

 

[thimios]

6JS6S

 

[EUVL]

https://www.radiomuseum.org/tubes/tube_ar300a.html

https://www.ebay.co.uk/itm/332797246911




Patrick

 

[petertub]

304TL with data sheet

 

[RJM1]

But yes the current from the filiment for the 6bk4 was also designed for 1.5ma. so no.
missed the edit time from my above post.

 

[jan.didden]

Maybe I am looking for a unicorn.
At 15mA and 4000V bias point, that's 60W.
All those compactrons have a Pa(max) of 40W, tops.

Jan

 

[EUVL]

Cascode ?
Or parallel.


Patrick

 

[jan.didden]

Tubes like the 20LF6 would be great if they had a bit more anode dissipation capability.

chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://frank.pocnet.net/sheets/135/2/20LF6.pdf

Jan