HT winding center tap question.

[diydidi]

Why do most guitar tube amps use a center tap on the HT winding? The tap is not grounded like the CT used for the heaters, but rather goes to a node created by two high voltage electrolytics.
Wouldnt a simple single HT winding have done it?

[nickb]

It's one way of ensuring the exactly half the HV supply voltage appears across each capacitor.

[diydidi]

I know Marshall uses a doubler circuit. Fender used sort of a half wave rect circuit with the CT grounded

[pdf64]

Have a read of The Valve Wizard
Voltage doublers are something different https://en.wikipedia.org/wiki/Voltage_doubler

[Dave H]

Fender used sort of a half wave rect circuit with the CT grounded

Which Fender circuits are you looking at? Can you post a schematic? The Fender amps I see with a center tap are two diode full wave rectifiers. The diodes conduct on alternate half cycles.