Comparing WE417A electron tube with open grid to pull up grid bias from cathode

At your risk. Take all safety precautions when working with any voltage or currant.


That sound similar.
Later addition. This electron tube at conditions stated did not sound as loud as expected. Cathode bias has not been tried. When driving a loudspeaker DL33 sounds louder or better. See newer posts.


The difference is the following:


When grid rectification effect takes place (see previous posts), bias decreases, anode current would decrease but it doesn't as the power supply has a high power resistor in series, average anode voltage increases. When loud misic passage finishes, electron tube gradually comes back to quiescent operating conditions. Typically comes back to 10mA, 90V, from say 9.7mA 120V from a loud music passage.


But not if grid is open or at space potential. Grid remains more negative as electrons have been attracted by it and have nowhere to go. (Like an electrometer). So release time is very large, infinite?
Average anode current or voltage stay like memory at say 9.7mA 120V. Ie electron tube remembers the music forte condition and remains at its automaticaly adjusted new quiescent condition.