cathode connection in directly heated triodes

[metebalci]

Hi,

Cathode circuit is connected to the point half in between the heater pins of directly heated triodes (such as 300B). I think this is to eliminate hum by connecting +Vh/2 to one and -Vh/2 to the other pin. Is it right ?

Is such a connection necessary if triode is heated with a DC supply ? will simply connecting the Vh (+) supply to one and cathode circuit to other pin of triode work ?

Thanks in advance.

MB

 

[Sch3mat1c]

Right on both counts. In fact tube data is traced with DC heaters and ground connected to a specific pin. I forget which though.

Tim

 

[metebalci]

Thank you so much...

MB