• 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

There's also the 6/38/40KD6's. Not quite as robust as the 6LF6 but close.
Maybe cheaper and more readily available. I've several I think. These tubes
were paralleled sometime 8 or more in HF linear amps during the CB craze in the US.
The 6LQ6 was also used in a lot of those amps. Always ran grounded grid.
 
  • Like
Reactions: 1 user
AX tech editor
Joined 2002
Paid Member
There's also the 6/38/40KD6's. Not quite as robust as the 6LF6 but close.
Maybe cheaper and more readily available. I've several I think. These tubes
were paralleled sometime 8 or more in HF linear amps during the CB craze in the US.
The 6LQ6 was also used in a lot of those amps. Always ran grounded grid.
I think the 36KD6 is used in the beveridge amp.

Jan
 
Yes 36KD6 in Beveridge amp.
schematic attached
 

Attachments

  • Bev 2SW_1 Amp Schematic Redrawn.png
    Bev 2SW_1 Amp Schematic Redrawn.png
    215.8 KB · Views: 75
Member
Joined 2008
Paid Member
Jan - What is a suggested max heating power? Thus far, I've found just under 50 that roughly meet your quoted min plate voltage and power but with considerable range of filament power consumption. If you wanted to take up pottery with your own kiln there are some that could help you along.
 

Attachments

  • 5946.pdf
    321.1 KB · Views: 33
AX tech editor
Joined 2002
Paid Member
I don't have a specific aim aside from 'as low as possible'.
Heater power would be a secondary requirement, the primary being 80W Pa (possibly two 40W in //) and 8kV max peak Vak.
I also would prefer a (beam) triode to avoid the complications of a G2 supply and possibly G2 arcing.

That 5946 looks interesting, appreciate the help!

Jan
 
I worry about sweep tubes for your use. Their peak voltage ratings are based on pulse conditions, and are anyway exceeded, or at least stretched, in your use. Their high perveance and big space charge come with a big heating power requirement, and is wasted in this use (they're almost turned off).

Sounding like a broken record, a transmitting valve is called for here, I'd submit. Something with a cathode surface designed for the 4KV anode voltage ion bombardment and an overall structure designed for 4KV all day every day. OK, I'll shut up about it now.

All good fortune,
Chris
 
  • Like
Reactions: 1 user
Member
Joined 2008
Paid Member
Earlier today I went down the CV list on Frank's site and focused only on power triodes (capital T) . Out of the 50 or so that can accomodate the high anode voltage, many had filament power demands that I had to assume are out of the question.

You might take a look at CV's - 28, 62, 92, 199, 240, 381, 446, 570, 1090, 1207, 1253, 1254, 1256, 1610, 1614, 1617, 2163
Many of these have equivalent numbers posted next with graphic data but the CV sheets mostly have the same layout so once you're used to them it's very quick to scan for the numbers you're interested in.

There are also some nice looking water cooled beasts around . : )
 

Attachments

  • 6C21.pdf
    967 KB · Views: 29
Jan check this schematics , since maybe this can be useful for your project , basically it represents principle how CRT cathode is linearly modulated with wide band video signal in countless nr. of colour TV set`s ,notice that there`s allways present one cathode very clean bias positive DC source , we R&TV repairsmans called that source simple as 200V line , principle is very simple , when video signal is not present on the driver transistors base than the driven cathode current is Ik=0uA , CRT screen is black , that also mean that cathode now stays on max.DC positive potencial relative to g1 which is grounded , that represent cutt-off point ,
the question is ; for your specific hybrid amp and for linear cathode drive but now with audio signal it is also necessary to have some suitable DC bias source or not ?
 

Attachments

  • LG CRT NECK BOARD.jpg
    LG CRT NECK BOARD.jpg
    86.4 KB · Views: 43
  • Cathode Bias.jpg
    Cathode Bias.jpg
    353.8 KB · Views: 44
Last edited:
Paralleling PL519 tubes would be the most interesting as these are available and affordable. Nice for experimenting.
7,5 kV should be about the max they can handle.
Why the need of increasing the voltage as i found that 3kV is more then enough to shake the house (concrete walls).
 
Last edited:
  • Like
Reactions: 1 user
Member
Joined 2008
Paid Member
Is that implied/allowed in the '3500 VDC' spec?
I do not have experience with tubes used in these voltage ranges , but in the little world I know the max voltages are given for steady state / quiescent or design centre operation unless specified otherwise. It's expected that with an inductive load , the voltage can swing up to 2x B+.
Until now I'd have assumed that industry nomenclature would be consistent across the board. Some of those sheets do make a distinction between max and max pulse or peak, but it's worth being absolutely sure.
I just sent an email to a vendor who should be able to confirm one way or the other.
If it's 100% sure that a 4KV max means it's safe to swing to 8KV unless specified on the sheet, things open up quite a bit.
 
  • Like
Reactions: 1 user
AX tech editor
Joined 2002
Paid Member
Earlier today I went down the CV list on Frank's site and focused only on power triodes (capital T) . Out of the 50 or so that can accomodate the high anode voltage, many had filament power demands that I had to assume are out of the question.

You might take a look at CV's - 28, 62, 92, 199, 240, 381, 446, 570, 1090, 1207, 1253, 1254, 1256, 1610, 1614, 1617, 2163
Many of these have equivalent numbers posted next with graphic data but the CV sheets mostly have the same layout so once you're used to them it's very quick to scan for the numbers you're interested in.

There are also some nice looking water cooled beasts around . : )
I made a rudimentary inventory as attached. It seems that the CV-1256 and its siblings are the most promising.
What I am wondering is the mechanical mounting of the tube. Am I right that the grid is in the center connected to a threaded insert.
How would I mount this tube on a chassis of some sort?

Jan
 

Attachments

  • CV-1256 mech.PNG
    CV-1256 mech.PNG
    134 KB · Views: 40
  • cv1256_01.jpg
    cv1256_01.jpg
    8.6 KB · Views: 39
  • xmit tubes.pdf
    406.8 KB · Views: 37
  • Like
Reactions: 1 user