[Waker]

So, what are the factors that influence tube life?  I can imagine running at high power output/volumes can hasten failure--speaker size, efficiency, room temp? And just how firm are the predicted lives of certain tubes, such as, I can expect 2000 hours before thinking of new--or can this be extended due to optimizing conditions for tubes?  I just had the KT-120 upgrade done for my ARC REF 210s, running Maggie 3.6s, two subs, 11.5 X 17 ft room.  What are some tricks that can extend tube life? eg check bias, provide extra ventilation?  Or, just enjoy and prepare to open wallet when indicated?     

[jtwrace]

This is why I cryo all my tubes.

[Steve]

So, what are the factors that influence tube life?  I can imagine running at high power output/volumes can hasten failure--speaker size, efficiency, room temp? And just how firm are the predicted lives of certain tubes, such as, I can expect 2000 hours before thinking of new--or can this be extended due to optimizing conditions for tubes?  I just had the KT-120 upgrade done for my ARC REF 210s, running Maggie 3.6s, two subs, 11.5 X 17 ft room.  What are some tricks that can extend tube life? eg check bias, provide extra ventilation?  Or, just enjoy and prepare to open wallet when indicated?   

Hi Waker,

Several factors attribute to long life.

1) As you mention limiting plate dissipation, as well as other element's dissipation, and lowering bulb temperature will tend to lengthen tube life. Use a muffin fan to cool the bulb if you desire.

2) Filament temperature, voltage applied, affects cathode life. If the cathode current is run in typical fashion, lowering the voltage about 5% below rated lengthens life as less cathode material (indirectly heated cathodes) evaporates. For example, a 6.3 volt filament run at 6 volts. As the cathode material evaporates, it condenses on other elements, such as grid 1. This can/will cause/increase grid 1 emission.

3) If possible avoid any conditions that will cause any element to overload. While plates may take a bit of time to cherry, screens and grids take much less time, and thus warp sooner.

In class A operation, such as preamplifiers and class A amplifiers, maximum plate dissipation usually occurs at idle, with no signal/power output. As the output wattage increases, the plate dissipation actually decreases as the average plate dissipation is equal to the average idle dissipation minus the average signal output in watts.

However, for class AB and B operation, plate dissipation increases as the input/output power level increases.

Hope this helps.

[FullRangeMan]

A red plate is sign of trouble.

[Pez]

People and manufacturers will claim a certain expectation of how long a tube will last, but it's always been my experience that it's a bit more unpredictable than that. I have had tubes last for years and I have had tubes go out in a matter of months. Like cars, sometimes you just get a lemon.

[Steve]

Nice picture Gustavo. Shows what not to do. With that said, there are a few tubes with graphite plates that can handle cherry color. But those few tubes are the exception.

Cheers Gustavo.

People and manufacturers will claim a certain expectation of how long a tube will last, but it's always been my experience that it's a bit more unpredictable than that. I have had tubes last for years and I have had tubes go out in a matter of months. Like cars, sometimes you just get a lemon.

Isn't that the truth Pez.

Cheers.

[FullRangeMan]

Thanks Steve, you most kind.

I do not like that standard tube amp manufacturer expectation ''3 years'', as tube life are measured in ''hours life''.
Which look to me as a mea culpa, or ''my amp is a tube eater''.

[rbwalt]

i have a music reference RM9SE amp and have no tube problems. i have had it now for 3.5 yrs. roger's amps are known for having long power tube life and drive tube life. what eats tubes are speakers that have a big dip in load impedance . say down to 4 or 2 ohms. this causes the amp to work into a mis-matched load. this happens when the speakers load impedance is not that of the amp's tap impedance. this over heats the tube making them gassy and unable to hold stable bias. now one can go to a lower tap but then will not be able to play as loud without clipping the amp. now roger's amps are able to drive speakers that have impedance's that drop sharply below the rated number of ohm's. they are capable of putting out more power as this happens. nice huh!

r.

[milford3]

Don't know if this wear is nornal or not.  Notice the clouding at the base of both tubes.
Tubes have fifty hours of play.

[FullRangeMan]

Milford3,
What wear are you referring??  The blur/spot at the tube base seems is the gas getter, placed during the tube manufacturing.

[milford3]

I replaced these tubes (6p6's) with EL34B's.  The base of the EL's is completly clear.  Just wondering if the pictured tubes are just wearing normally?

[SET Man]

I replaced these tubes (6p6's) with EL34B's.  The base of the EL's is completly clear.  Just wondering if the pictured tubes are just wearing normally?

Hey!

   Those tubes pictured look normal to me. If talking about the silver colored coating on the bottom of those tubes... these are "getter". A thin coating that help absorb gases in the tube.

    Of course the EL34 tube's base is clear because the getter is on the top of the tube  Different type of tubes have getter at different area of the tube... sometime same type of tube have getter at different place, depend on the manufacturer's design.

    You should be worry if the getter start to turn white, that is a sign of tube having a problem or worst, a leak. As long as it stay dark silver in color you are OK. 

Take care,
Buddy