As I understand it, that is not entirely true. An example is the trace amounts of silicon in the nickle of most indirectly-heated cathodes. The silicon poisons the emmissive material, slowly increasing the noise and resistance and leading to was called "sleeping sickness" back in the day. The term "interface resistance" is also used. This became a serious problem when tubes were used for computers, until high-purity nickel became available. The 5965 is one of many tubes made specifically for digital use by using these high-purity nickel alloys. It is mentioned in the data sheets of most such tubes.
from frends on AD1 Telefunken
The harp filament (similar to that of the 2A3 monoplate) which worked, however, at a very low temperature thanks to the application of the emitting layer by vaporization during the emptying/activation phase. It is a fact that even after many years, you never see grid currents, and the temperatures of use are enormously lower. a 2A3 monoplate, filament only heats up a lot. An AD1 TFK, no. These continuous cooling and heating cycles do not help the vacuum seal, especially if the construction is hasty as on the American ones. I assume that the problem lies in the creation of the connections in the stem which should be made with copper-coated nickel steel wires (Dumet) and which should have "approximately" the same expansion coefficient as the glass used. This is what creates problems. The quality of the glass, the Dumet wire and the process itself require considerable attention.
The harp filament (similar to that of the 2A3 monoplate) which worked, however, at a very low temperature thanks to the application of the emitting layer by vaporization during the emptying/activation phase. It is a fact that even after many years, you never see grid currents, and the temperatures of use are enormously lower. a 2A3 monoplate, filament only heats up a lot. An AD1 TFK, no. These continuous cooling and heating cycles do not help the vacuum seal, especially if the construction is hasty as on the American ones. I assume that the problem lies in the creation of the connections in the stem which should be made with copper-coated nickel steel wires (Dumet) and which should have "approximately" the same expansion coefficient as the glass used. This is what creates problems. The quality of the glass, the Dumet wire and the process itself require considerable attention.
You would definitely appreciate direct heating to emitting oxides. No thorium tungsten.
So: 300B, 2A3, 45, PX4 and WE VT52.
nicoch58,
Definitely appreciate?
What is it about direct heating 300B, 2A3, 45, etc. that I would definitely appreciate Versus emitting oxides?
Better sounding amplifiers, or what?
What is it about direct heating 300B, 2A3, 45, etc. that I would definitely appreciate versus thorium tungsten such as the WE 212E?
Better sounding amplifiers, or what?
And which designs . . . AC filaments, Or DC filaments on all those DHTs?
I designed, built, and listened to 300B and 2A3 SE and PP amplifiers.
I designed, built, and listened to 45 and SE and amplifiers.
Some of them used AC powered filaments, and some used DC powered filaments.
Sure . . . I only listened to thoriated tungsten DHT SE amplifiers that others designed and built; including the WE212E SE.
That was more of an amplifier that I wanted to go to the trouble to buy parts, build, and lift the mono-blocks (far beyond my Doctor's recommended Hernia limit for lifting).
Perhaps your initial statement was a Generalization?
Definitely appreciate?
What is it about direct heating 300B, 2A3, 45, etc. that I would definitely appreciate Versus emitting oxides?
Better sounding amplifiers, or what?
What is it about direct heating 300B, 2A3, 45, etc. that I would definitely appreciate versus thorium tungsten such as the WE 212E?
Better sounding amplifiers, or what?
And which designs . . . AC filaments, Or DC filaments on all those DHTs?
I designed, built, and listened to 300B and 2A3 SE and PP amplifiers.
I designed, built, and listened to 45 and SE and amplifiers.
Some of them used AC powered filaments, and some used DC powered filaments.
Sure . . . I only listened to thoriated tungsten DHT SE amplifiers that others designed and built; including the WE212E SE.
That was more of an amplifier that I wanted to go to the trouble to buy parts, build, and lift the mono-blocks (far beyond my Doctor's recommended Hernia limit for lifting).
Perhaps your initial statement was a Generalization?
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Why did RCA stop making the mono-plate 2A3 that had 24 filament wires?
Was it the fact that the filament wires were so thin that they were fragile and often broke?
Was it the fact that the tube was very expensive to build?
According to some that have actually heard those rare tubes, I do not think it was because they sounded bad, they sounded good.
Over many decades, I have experienced very few tube failures in any of my amplifiers, no matter whether I or somebody else designed them.
Lucky me.
What do I do when a tube fails? I check for the cause, if it is the tubes fault . . . I replace it.
Simple.
Nobody said tube amplifiers were cheap.
Frank Reps said: "Cheap is not good, and good is not cheap"
Does anybody need a cheap hobby . . . then take up Skiing, or car racing.
Was it the fact that the filament wires were so thin that they were fragile and often broke?
Was it the fact that the tube was very expensive to build?
According to some that have actually heard those rare tubes, I do not think it was because they sounded bad, they sounded good.
Over many decades, I have experienced very few tube failures in any of my amplifiers, no matter whether I or somebody else designed them.
Lucky me.
What do I do when a tube fails? I check for the cause, if it is the tubes fault . . . I replace it.
Simple.
Nobody said tube amplifiers were cheap.
Frank Reps said: "Cheap is not good, and good is not cheap"
Does anybody need a cheap hobby . . . then take up Skiing, or car racing.
I used AC on 300B and Rod set as filament bias on the two pair 10Y( thorium )got from AndyEvans
n"The TFK AD1, as we know had no lifetime issue. So it was not impossible, but I think they doted the cathodes also slightly radio active. We would not dream of that today, of course. So what did they do.... The cathode wires were initially not Barium Oxide coated. I have a 1930's RE604 lab model here, with the pill not activated. They used nickel alloy. The Barium depot is inside a 'pill' in a cavity in the middle of the anode, at the inside. You can also see from that cavity from the outside. When the tube is ready build, the Barium pill gets evaporated by heat, and Barium is spread all over the tube, also to the heater wire. Then, by electric methods, combines with heat, the residue gets removed, and a thin layers stays on the heater. Also Barium as we know is a good gettering material. All in all, a clever, but very difficult process. This results in remarkable heater efficiency, but on the sacrifice of having not much Barium on the cathode. Yet they did it, don't ask me how, lifetime was good, and no electrode leakage. The Philips and Tungsram types are not fully free of electrode leakage problems. Valvo are very good also. The original Telefunken AD1 had 0,9A and a condensed Barium plating.
nicoch58,
You appreciate technology. So do I.
So much has been forgotten, or is no longer used. What a pity.
Good technology was/is a sign of success.
Bell Labs, Tektronix Labs, and others . . . RIP.
Appreciating listening sessions is another aspect, it can give thumbs up, thumbs down, or indifference to the sound.
Success or not?
How about the success of being pleased and relaxed with the music that is played back?
When a group listening session seems to be nothing but tension and serious analysis . . .
I say something like: "That clarinetist is using a # 2 Reed, he should be using a # 1 Reed."
From a famous Author: "Enjoy the Music".
You appreciate technology. So do I.
So much has been forgotten, or is no longer used. What a pity.
Good technology was/is a sign of success.
Bell Labs, Tektronix Labs, and others . . . RIP.
Appreciating listening sessions is another aspect, it can give thumbs up, thumbs down, or indifference to the sound.
Success or not?
How about the success of being pleased and relaxed with the music that is played back?
When a group listening session seems to be nothing but tension and serious analysis . . .
I say something like: "That clarinetist is using a # 2 Reed, he should be using a # 1 Reed."
From a famous Author: "Enjoy the Music".
