• 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.

increase live 211 tube

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The main detriment to vacuum tubes is heat generated by plate dissipation. The 211s have a 100 watt maximum dissipation rating. (Plate voltage x plate current) Limiting that to an acceptable level (80%?) is the most you can do. Acceptable levels is a trade off between sonics, power out and useful life.

Do not run the filaments on low voltage! From everything I have read filament chemistry requires a specific temperature range. Operating outside that range will shorten the emission life. Far outside will be even worse permanently damaging the tube through "filament poisoning".

Delayed application of high voltage is a debatable issue for many. It stems from high power transmitting tube usage where filaments are subject to ion bombardment from very high potentials. Exactly what constitutes "high" is the point of contention. 1KV is the generally accepted number, but it can vary depending on the particular tube. 211s and 845s are fast heating tubes who's filament reaches operating temperature in one second or less and typically are operated at 1200 plate volts or less.

So is it needed with these? I've seen several amplifiers using these tube types that don't delay HV and they don't suffer premature failure. In my opinion delay is not necessary assuming the filaments are never left off with HV applied. On the other hand delaying HV can't hurt. If you're short on tubes, cash or just want to rest easier, then delay it. But in a properly working amplifier I don't think it will, by its self, extend tube life. Remember it's the heat from dissipation that does the aging.
 
211 life

Hollow I have a friend that worked in the last in high power transmission tubes 1kw and this tubes always were at 25% of the filament when B+ was off and before to connect voltage to the plate increasing the filament voltage in steps to the operating voltage, this tubes worked for more than 25 years, this is why that maybe if use in the 211 filaments can extend the life of the expensive tubes as ELROG.

I think that the premature break of the tubes are normally by the stress failure of the filaments that for cathode deteriorate, but this is my think, I have not read information about this study.
 
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211 has thoriated tungsten (TT) filament.

I'm in love with these tubes tone (I also use 10/10Y/VT-25, 841/VT-51, 801/801a/VT-62 tubes), but its requires special care.

TT filament glow at very hot temperature -about 2000K !!!-, and his cold resistance is much smaller, than "operating" resistance.
Every On state stressed this type filament with large inrush current, thus smooth ramping is necessary (I regularly use Rod Coleman reagulators).

Due to the "Miller-Larson effect" every On/Off state "eating" this type filament, grow its lenght and make it thinner up to the interruption.

Miller-Larson effect:

Whitaker: Power Vacuum Tubes Handbook 10.4.4.
https://books.google.hu/books?id=TF...E#v=onepage&q="Miller-Larson Effect "&f=false

Thoriated Tungsten Filament power cycling

Thick filament -as 211 has- slowly run out than small tubes one, but failure surely come sooner or later.

One possibile solution is always use this type tubes ON state (filament glow, anode current flow), but it's not a cheap game.

The most important thing: DON'T move this tubes until warmer than lukewarm!
TT filament is very fragile.
 
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