Is "low power" setting on an amp harder on tubes?

WoodyStrat

Member
Messages
2,112
I always have my 16 watt amp (2 6V6 Valvetrain Trenton) set to the low power or 6 watt setting. Would this cause the tube life to be reduced? It seems as if I replace tubes more often since adopting this behavior.
 

Billm

Member
Messages
574
It depends on how they do it. A schematic would help. The usual way is to switch to triode mode--connecting the screen grids to the plates. That increases screen current, but makes the tube less efficient overall. I could see it perhaps wearing out the screen grid more quickly, but even that is just a guess, because the screen is a much smaller target for the electrons than the plate.

Since this is a cathode-biased amp, you can check pretty easily to see if the tube is working harder, although less efficiently, in triode mode. Put a voltmeter on the cathode resistor and see if the voltage goes up when you switch to low power mode.
 

WoodyStrat

Member
Messages
2,112
It depends on how they do it. A schematic would help. The usual way is to switch to triode mode--connecting the screen grids to the plates. That increases screen current, but makes the tube less efficient overall. I could see it perhaps wearing out the screen grid more quickly, but even that is just a guess, because the screen is a much smaller target for the electrons than the plate.

Since this is a cathode-biased amp, you can check pretty easily to see if the tube is working harder, although less efficiently, in triode mode. Put a voltmeter on the cathode resistor and see if the voltage goes up when you switch to low power mode.
Thanks Bill, I will look into it!
 




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