How to build a gradual tension rise psu for tube designs ?

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innercityman

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Hi all audio geeks ! :D

I've read somewhere that to preserve tubes life, using a psu that gradually rise the tension would improve their longivety.

Could someone tell me more about it and explain the concept ?
 

abbey road d enfer

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innercityman said:
I've read somewhere that to preserve tubes life, using a psu that gradually rise the tension would improve their longivety.

Could someone tell me more about it and explain the concept ?
I believe it's a myth when it comes to the type of products used in audio.
Thousands of guitar amps receive the schock treatment when switched from standby to on.
 

emrr

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Myth.

I just restored a large early 1930's system that still had very very old tubes in it, probably put there in the 1940's.  The system was in use in the 1990's. 

Operating voltage is 300VDC, at turn-on the initial voltage from the tube rectified PSU was about 580VDC, drops to 300 once the filaments warm up. 

None of the tubes were bad, most were reasonably strong and in range for expected current consumption, one tube in every channel consumed 26mA. 
 

innercityman

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Operating voltage is 300VDC, at turn-on the initial voltage from the tube rectified PSU was about 580VDC, drops to 300 once the filaments warm up. 

None of the tubes were bad, most were reasonably strong and in range for expected current consumption, one tube in every channel consumed 26mA.

I believe it's a myth when it comes to the type of products used in audio.
Thousands of guitar amps receive the schock treatment when switched from standby to on.

Thanks for sharing your experiences guys, really appreciated.

I was asking because a guy is actually developing for commercial purpose, a version of the Redd 47 (yes, another one...  ::)) and he puts in the front the fact that he developed a special gradual tension rise PSU that is supposed to preserve tubes from "aging". And he highlights this fact as a sort of a must-have option.
 

trobbins

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There can be amp circuits where a nominal rise time of B+ can cause the output stage valve(s) to conduct heavily whilst coupling caps and other long time-constant paths attain their continuous operating conditions. If the output stage valve cathode is asked to conduct at its current limited capability, and the temperature of that cathode is still rising then plausibly there is stress on the cathode material/surface due to temperature hot spots. I also recall there may be stress situations for screens under certain conditions.

This would be a complex issues to analyse as there are so many different amp circuits, as well as power supply configurations and how fast and at what time they start to raise B+. Perhaps easier to appreciate by just capturing the dynamic start up power dissipation conditions for an output stage valve

Whether a relatively slow B+ rise could reduce any such stress situation is not a direct outcome, and would require justification imho (rather than just advertising blurb).
 

Heikki

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There is common problem in guitar amps with direct coupled cathode followers where there might be arcing between electrodes when the amp is turned on. Easy fix is presented here: The Valve Wizard

Anyone experiencing short tube life I would look if there's something wrong with the design.
 

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