Hello everyone.
In my 813 Push Pull amp ( Pentode connected, Fixed bias, DC filament , with polarity switch)
Where do I connect G3 (to the cathode) ?
And, where do I reference the cathode to 0V (earth) , or should I create a pseudo earth with resistors across the filament?
In my 813 Push Pull amp ( Pentode connected, Fixed bias, DC filament , with polarity switch)
Where do I connect G3 (to the cathode) ?
And, where do I reference the cathode to 0V (earth) , or should I create a pseudo earth with resistors across the filament?
Creating a centre-tap + humpot is only needed for rectified-only DC feed. Low noise current-feed filament supplies (mine, for exampe) allow better sound by returning only the negative side to ground,
G3 is usually grounded, or, as you infer connected the k, it depends on what k is connected to. G3, the suppressor grid is there to stop electrons being dislodged from the anode & attracted to the screen grid by secondary emission. See - https://valvewizard.co.uk/pentode.html
Andy.
Andy.
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It's a big directly-heated beam tetrode, according to the datasheet on http://www.r-type.org/exhib/aaq0393.htm
According to page 3 of the datasheet, g3 should be connected to the negative side of the filament/directly-heated cathode when you use DC heater power. In your case, that would mean the negative side of the input of the heater polarity switch.
According to page 3 of the datasheet, g3 should be connected to the negative side of the filament/directly-heated cathode when you use DC heater power. In your case, that would mean the negative side of the input of the heater polarity switch.