Center Tap Full Wave Rectifier - CT tied to DC instead of ground

[Pat Maki]

I'm repairing an Altec 525 power supply as a means to learn more about tube mic circuits. All the reading I've done on CT full wave rectifiers show the CT going to ground. Can someone please explain why the CT of the top secondary is referenced to 260V of rectified DC from the other secondary in this circuit? Why doesn't the CT just go to ground?

 

[shabtek]

There is a limited permissible cathode to heater voltage, data sheet might indicate it…the cathode is at 200vdc in this schematic/cathode follower configuration…in a typical plate follower the cathode will be close to 0vdc and filament supply can be referenced to 0v

 

[scott2000]

Why doesn't the CT just go to ground?

Look up heater elevation... elevating heaters....
I pretty much always do it.... Feels like a cheat code for noise most of the time...