elevated tube heater supplies ?

[KIDVOX]

this is somthing i know is used with a few tube rectifiers. i have also seen it referenced with cascaded triodes. could some one please give a simple example circuit with a brief explanation, ie function and advantags. i hate feeling ignorant which i do at the moment

 

[metalockpick]

Sorry I can't give you a schematic, but here's an example: you've seen filament supplies with either a grounded center tap from the power transformer or two resistors that go from each filament to ground. That's a ground referenced filament. Now, imagine that instead of hooking the resistors or the center tap to ground, you connect them to a positive DC supply, to hold that voltage above ground. In cases where the cathode voltage is high, this type of circuit can be beneficial by keeping the cathode voltage and the reference voltage closer. One example is that electro harmonix 12AX7EH Tubes don't work well in guitar amp phase inverters or cathode followers because of the high voltages on the cathodes. Referencing the filaments to (higher) DC voltages will fix that issue.

 

[scott2000]

please give a simple example circuit

Can't remember if this video explains it well. Some of his videos are pretty good though...

 

[KIDVOX]

thanks mate. very helpful. ill check it out later.

 

[KIDVOX]

read the posts, watched the video, looked at the schematic. now i understand. thanks for removing my ignorance folks.